What are the FAQs and How-Tos for Physics Forums?

[micromass]

NOTE: Some of these FAQs need to be updated for PF 4.0.

This thread contains tutorials and frequently asked questions about the Physics Forums website.

Contents:

1. How to Make a New Post Definitely needs a complete overhaul
2. How to Type Mathematical Equations
3. Why Has Nobody Answered My Post?
4. Suggestions in Forum Feedback
5. Known Bugs and Features Definitely needs a complete overhaul
6. How to Ask for Homework Help
7. About PF's Policy on Speculative Discussions ("New Theories," etc.)
8. Some information on physicsforums and its history
9. Physicsforums medals and gurus
10. Copy-and-paste math symbols

The following technical FAQs are available:
https://www.physicsforums.com/forumdisplay.php?f=209
https://www.physicsforums.com/forumdisplay.php?f=210
https://www.physicsforums.com/forumdisplay.php?f=207
Evolution

 

[micromass]

How to make a post at physicsforums

NOTE: This post needs a complete overhaul for PF 4.0.

Important: When you want to ask a question, do not send a visitor message, do not ask in the library, do not post to another existing thread. You need to start a new thread.

Getting started: To start a new thread at this forum, you first need to go to the appropriate forum. You'll find a list of forums at our main page at https://www.physicsforums.com. When you have reached an appropriate forum, you click the "NEW TOPIC" button as displayed in the image below:

If you do not wish to start a new thread, but merely reply to a post, then you should first go to the thread you wish to reply to. Then click the "QUOTE" button that is circled in the image below:

Do not use the "Report" button for posting replies (the report button is the one which is crossed out in the previous image). This button sends a message to the mentors (moderators), and is used for reporting posts that you think violate our rules.

Some important remarks:
1) Homework questions and homework-style questions always belong in the homework forums: https://www.physicsforums.com/forumdisplay.php?f=152

2) When posting in the homework forums and you start a new thread, the following will always appear:

[NOPARSE][h2]Homework Statement [/h2][/NOPARSE]
[NOPARSE][h2]Homework Equations[/h2][/NOPARSE]
[NOPARSE][h2]The Attempt at a Solution[/h2][/NOPARSE]

This is called the homework template. Do not delete it, otherwise your post may be removed. Rather fill it in with useful information.

Some useful pictures for future reference:
The following picture will be denoted by the letter A:

The following picture will be denoted by the letter B:

The following picture will be denoted by the letter C:

For example, if I refer to A.6, then I refer to number 6 on picture A. This is the "Submit New Thread" button.

Basics of posting: When you click on the "NEW TOPIC" or "NEW REPLY" button, then you will be taken to a page that looks like image A (there might be differences). Below image A, we will find image C.

Obviously, the thread title should be written in A.1. Be sure to make a descriptive thread title! Thread with titles like "Help needed ASAP" will be deleted.

The actual contents of the post should be written in A.3. We will describe later how to make nice edits to the post.

Once you are done, you may submit your thread by clicking on A.6 or C.6. However, it is highly recommended to first preview your post. This is of course done by clicking A.7 or C.7. This will show you the post exactly how it would appear.

A known bug: If you make a new thread in the homework forums and click preview, then the homework template will be added again to your post. This is a known bug that we are unable to solve. It is perfectly ok to delete that extra homework template.

How to type mathematical symbols? There are two ways to type mathematical symbols. The first is by looking at A.5. This is a list of commonly used symbols. Just clicking on a symbol will add it to your post. If you need a symbol that you don't see in that box, you can try to find it in post #11, or on http://tlt.its.psu.edu/suggestions/international/bylanguage/mathchart.html .

The most common way to post mathematical symbols is by using LaTeX. Clicking on B.34 will give you a list of mathematical symbols. Clicking on such a symbol will print the formula of the symbol on the screen enclosed in [NOPARSE]$...$[/NOPARSE] tags.

For a very extensive LaTeX guide, please read: https://www.physicsforums.com/showthread.php?t=546968

Note: Buttons A.5 and B.34 are not present in all forums.

How to change the look of the text?

Changing font/textsize/text color: Please do not use a nonstandard font, textsize of text color at this forum. The rules state:

When posting a new topic do not use the CAPS lock (all-CAPS), bold, oversized, non-standard, or brightly colored fonts, or any combination thereof. They are hard to read and are considered yelling. When replying in an existing topic it is fine to use CAPS or bold to highlight main points.

Using bold: To use bold, click button B.12. When doing so, the following will appear on your screen:

[NOPARSE][B][/B][/NOPARSE]

Typing between these tags will yield bolded text. For example:

This is [NOPARSE][B]bold[/B][/NOPARSE] text.

will result in:

This is bold text.

Please do not bold your entire post, the rules state:

When posting a new topic do not use the CAPS lock (all-CAPS), bold, oversized, non-standard, or brightly colored fonts, or any combination thereof. They are hard to read and are considered yelling. When replying in an existing topic it is fine to use CAPS or bold to highlight main points.

Using italics: To use italics, click button B.13. Type between the tags to make the text italic
Typing between these tags will yield italic text. For example:

This is [NOPARSE][I]italic[/I][/NOPARSE] text.

will result in:

This is italic text.

Underlining: To use underlining, click button B.14. Type between the tags to make the text underlined.

Typing between these tags will yield bolded text. For example:

This is [NOPARSE][U]underlined[/U][/NOPARSE] text.

will result in:

This is underlined text.

Subscripts and supscripts: To type text like this: _subscript or ^supscript, use B.29 or B.30. This will again print certain tags on your screen. Typing between these tags will make subscript or supscript.

For example:

[NOPARSE]x[SUB]2[/SUB] and a[SUP]2[/SUP].[/NOPARSE]

will give

x₂ and a².

Do not use this in combination with [NOPARSE]$...$[/NOPARSE].

Adding smileys: Smileys can be added by clicking button B.5. To disable smileys throughout your entire post, click C.2

Spoiler tags: To add spoiler tags, click button B.31. Typing between these tags will make the text disappear until it is highlighted. For example:

[NOPARSE][SPOILER]Highlight me to see me![/SPOILER][/NOPARSE]

gives

Spoiler

Highlight me to see me!

Strike-through text: To create text with a line through, click B.33. Typing between the tags which appear will present the text striked through. For example

[NOPARSE][STRIKE]This is wrong[/STRIKE] This is right.[/NOPARSE]

will give

[STRIKE]This is wrong[/STRIKE] This is right.
​

Changing the text-flow

Numbering/Itemizing To create a number or itemizing, click B.18 (for numbering) or B.19 (for itemizing). To create a new item, type [NOPARSE][*][/NOPARSE] with then the text. For example:

[NOPARSE][LIST=1][/NOPARSE]
[NOPARSE][*] First item.[/NOPARSE]
[NOPARSE][*] Second item.[/NOPARSE]
[NOPARSE][/LIST][/NOPARSE]

will give

1. First item.
2. Second item.

While,

[NOPARSE][LIST][/NOPARSE]
[NOPARSE][*] First item.[/NOPARSE]
[NOPARSE][*] Second item.[/NOPARSE]
[NOPARSE][/LIST][/NOPARSE]

will give

• First item.
• Second item.

Centering/aligning left/aligning right To align a text to the left, click B.15. To center a text, click B.16. To align a text to the right, click B.17. Type between the tags which appear.

For example

This is normal.
[NOPARSE][LEFT]This is aligned to the left.[/LEFT][/NOPARSE]
[NOPARSE][CENTER]This is centered.[/CENTER][/NOPARSE]
[NOPARSE][RIGHT]This is aligned to the right[/RIGHT][/NOPARSE]

gives

This is normal.

This is aligned to the left.​

This is centered.​

This is aligned to the right​

Indenting: To indent a text, click on B.21. Typing between the tags will indent the text. For example

This is normal.
[NOPARSE][INDENT]This is indented[/INDENT][/NOPARSE]
[NOPARSE][INDENT][INDENT]This is indented twice[/INDENT][/INDENT][/NOPARSE]

gives

This is normal.

This is indented

This is indented twice​

Adding stuff to your post:
Adding images: To add images, click on B.25. Type the link between the tags (or in the pop-up that appears) to add the image. For example:

[NOPARSE][PLAIN][PLAIN]http://chzlolcats.files.wordpress.com/2007/01/funny-pictures-kitten-has-flavor.jpg[/PLAIN]  [/NOPARSE]

gives

[PLAIN]http://chzlolcats.files.wordpress.com/2007/01/funny-pictures-kitten-has-flavor.jpg

Posting youtube videos: To post a youtube video, click the B.32 button. Between the tags, you should type only the end of the link, that is: the code which appears after the =. For example

[NOPARSE]
https://www.youtube.com/watch?v=dQw4w9WgXcQ 
[/NOPARSE]

gives

https://www.youtube.com/watch?v=dQw4w9WgXcQ

Adding attachments: To add an attachment, click on B.6 or C.3. The following pop-up should appear:

In 1 and 2, you can upload the attachment. To upload it from your computer, click "Browse" in 1 and select the file. Then click "Upload". To select a file that is already online, paste the link of the file/image in 2 and click Upload.

The uploaded attachments should appear in 3. Clicking the attachment will open the attachment in a new window. For images, you can use this to find a link to the image. You can then add this image to the post with the [NOPARSE]http://... [/NOPARSE] tags, as explained before.

Finally, 4 gives a list of file extensions and file limits for which uploading is allowed.

Note: it is better for our server not to upload attachments here, but rather to upload them to another website and then linking them here. So please take care with your attachments.

Adding code tags: To present programming code at this forum, it is nice to do so while using code tags. To make code tags click on B.27 and type between them.

[NOPARSE][CODE]This is between code tags

[/NOPARSE]
[/CODE]

yields

This is between code tags

Other options:

Cut/copy/paste: To cut something, click on button B.7. This deletes the text, but saves it to the clipboard so you can paste it later.
To copy text, click on button B.8. This saves the text to the clipboard without deleting it.
To paste text which was cut or copied, click on B.9.

Undo/redo: To undo a certain action, click on B.10. To redo the action, click on B.11.
​

The authors of this FAQ were

• AlephZero
• Borek
• Evo
• Fredrik
• jtbell
• micromass
• Redbelly98
• tiny-tim

 

[micromass]

Re: Physicsforums FAQ

How to type mathematical equations here?
Updated document here
https://www.physicsforums.com/help/latexhelp/

​

As of today, LaTeX doesn't work under old Opera.​

​

Note: LaTeX works only in a web browser, not in the PF apps for iOS (iPhone, iPad) or Android.​

​

Getting started: Those fancy mathematical symbols are being made with something called LaTeX. It's easy to include LaTeX code in your posts at Physics Forums. You just need to type the LaTeX code that produces the formula you want between [itеx] and [/itеx]. For example, if you type either​

​

$y = a x^2 + bx + c$​

​

or​

​

$y = a x^2 + bx + c$​

​

the result will be​

​

$y = a x^2 + bx + c$.​

​

Mark44 note: I find it easier to use the # pairs instead of the itex tags for inline LaTeX, and the $ pairs instead of the tex tags for standalone LaTeX.​

​

Alternatively, you can type LaTeX code between [tеx] and [/tex]. These tags do essentially the same thing as the itex tags, but the formula will be displayed indented on a separate line. So if you type​

​

$$\Delta \theta = \omega_0 t + \frac{1}{2} \alpha t^2$$ ​

​

the result will be​

​

$$\Delta \theta = \omega_0 t + \frac{1}{2} \alpha t^2$$​

​

For the ones already familiar with LaTeX: [itex][/itex] tags are analogous to ## pairs, and [tex][/tex] tags are analogous to $$ pairs.​

​

The easiest way to learn LaTeX is to see what others have done. If you see a post with a nice equation in it, just click QUOTE (at the bottom of the post) to see what the author did.​

​

Simplified tags: Instead of typing [itеx] and [/itеx], you can type $and$ (i.e., at the beginning and end of your expression). Instead of typing [tеx] and [/tеx], you can type $$ and $$.​

​

For example​

​

The equation $x+2=3$ implies $$x=1.$$​

​

Will yield:​

​

The equation $x+2=3$ implies $$x=1.$$​

Punctuation: If you're using tex tags and you want a comma or a period after your formula, you should put it before the closing tex tag. If you're using itex tags, it doesn't matter if you put it before or after the closing itex tag. Also, when you use tex tags, the software will put a blank line before and after the formula. So you don't have to type any line breaks before the opening tex tag or after the closing tex tag. However, you can type a single line break before a tex tag without changing the output. The following example illustrates these ideas.​

​

Let $f:\mathbb R\rightarrow\mathbb R$ be the function defined by​

$$f(x)=x^2,$$ for all $x\in\mathbb R$.​

​

This produces:​

​

Let $f:\mathbb R\rightarrow\mathbb R$ be the function defined by​

$$f(x)=x^2,$$ for all $x\in\mathbb R$.​

​

Important bug: (may not be true any more, we haven't tested this yet) vBulletin (the forum software) has a feature that will sometimes break correct LaTeX code. If you type more than 50 characters without a space, vBulletin will insert one for you after the 50th character. This will break the code unless you're lucky enough to have the space end up before a LaTeX command rather than in the middle of it. To prevent this from happening, you will have to make sure that your code contains a space at least once every 50 characters. If you often write long pieces of LaTeX code, you may want to start to routinely type extra spaces that will be ignored by the LaTeX processor, for example before equality signs and LaTeX commands that aren't arguments of other LaTeX commands.​

​

Another bug is that if you edit a post that contains LaTeX code without going to advanced edit mode, the code will not be parsed when you view the thread immediately after saving the changes. The math looks fine to everyone else, but you will need to refresh the page (in your browser) to see the math again.​

A very short introduction to LaTeX

The previous section explains how to include LaTeX code in posts, but it doesn't explain LaTeX. So in this section, we will explain how to type common mathematical formulas in LaTeX.​

​

Special characters: The following characters have a special meaning in LaTeX: # $ % { } _ ^ \ ~​

So if you want one of these characters to be displayed, you must type the code for the symbol rather than the symbol itself. The LaTeX codes for the first six of these symbols are: \# \$ \% \{ \} \_​

​

Spacing: LaTeX ignores most of the spaces and end-of-line characters you type. For example​

​

x y​

z​

​

will produce​

$$x y$$​

$$<div style="margin-left: 20px">z​</div>$$

​

There is a number of LaTeX commands that you can use to control the horizontal distance between characters. \ (followed by a space) or ~ inserts a space. The difference is that ~ ensures that LaTeX will not break the line at that space. \, inserts a small space. \! inserts a small negative space (moves the cursor a little to the left). \quad and \qquad insert larger spaces. You can also use the [FONT=Courier New]\hspace command to explicitly specify the width of the space. For example,​

​

[FONT=Courier New]a\!b\,c\ d~e\quad f\qquad g\ \ \ \ h~~~~i\hspace{20mm}j​

​

gives $$a\!b\,c\ d~e\quad f\qquad g\ \ \ \ h~~~~i\hspace{20mm}j$$​

To get the result $f(x)=1\ \text{if} \ x>0$, you can't just type​

​

[FONT=Courier New]f(x)=1 if x>0​

​

The result will be ugly: $f(x)=1 if x>0$. Any of these codes will do a better job:​

​

[FONT=Courier New]f(x)=1\ \text{if}\ x>0​

[FONT=Courier New]f(x)=1~\text{if}~x>0​

[FONT=Courier New]f(x)=1\text{ if }x>0​

​

These are the results:​

​

$f(x)=1\ \text{if}\ x>0$​

$f(x)=1~\text{if}~x>0$​

$f(x)=1\text{ if }x>0$​

​

The [FONT=Courier New]\text command tells LaTeX to interpret what comes next as text, instead of as variables.​

​

[B]Subscripts and superscripts:[/B] To put a subscript on a variable, use the [FONT=Courier New]_ symbol. To put a superscript on a variable, use the [FONT=Courier New]^ symbol. For example, if you type​

​

[FONT=Courier New]x_y,\ x^y​

​

the result is $x_y,\ x^y$. If you want to display just the subscript or the superscript, and not the variable, type [FONT=Courier New]{} where the variable would normally be. This trick is also useful when the horizontal positioning of the indices is important, as in the following example.​

​

[FONT=Courier New]\Lambda^\mu_\nu,\ \Lambda_\nu^\mu,\ \Lambda^\mu{}_\nu,\ \Lambda_\nu{}^\mu​

​

[tex]​

\Lambda^\mu_\nu,\ \Lambda_\nu^\mu,\ \Lambda^\mu{}_\nu,\ \Lambda_\nu{}^\mu​

[/tex]​

Subscripts and superscripts work with integrals, limits, summations, and several other symbols. For example,​

​

[FONT=Courier New]\lim_{n\rightarrow +\infty} {\frac{\sin(x)}{x}}​

​

will give us​

$$\lim_{n\rightarrow +\infty} {\frac{\sin(x)}{x}}$$​

If you do the same thing between itex tags, then you get $\lim_{n\rightarrow +\infty} {\frac{\sin(x)}{x}}$. The subscript is written next to the limit instead of beneath it. If you don't like this, you can use the [FONT=Courier New]\displaystyle command. For example,​

​

[FONT=Courier New]\displaystyle\lim_{n\rightarrow +\infty} {\frac{\sin(x)}{x}}​

​

will give $\displaystyle\lim_{n\rightarrow +\infty} {\frac{\sin(x)}{x}}$.​

​

[B]Grouping:[/B] By default, most LaTeX commands act only on the first character or command on its right. ([FONT=Courier New]\displaystyle is one of the exceptions). To make them act on longer pieces of input, use curly brackets [FONT=Courier New]{ }. For example​

​

[FONT=Courier New]x^{10}+x^10​

​

gives $x^{10}+x^10$. If you want to limit the scope of a [FONT=Courier New]\displaystyle command, place the curly brackets as in this example​

​

[FONT=Courier New]\lim_n x_n={\displaystyle\lim_n x_n}=\lim_n x_n​

​

The result is $\lim_n x_n={\displaystyle\lim_n x_n}=\lim_n x_n$.​

​

You can nest brackets within brackets as deeply as you want to build up a complicated expression. For example​

​

[FONT=Courier New]\sqrt{1+\sqrt{1+\sqrt{1+x}}}​

​

gives $\sqrt{1+\sqrt{1+\sqrt{1+x}}}$.​

​

[B]Delimiters:[/B] The delimiters $(~),[~], \{~\}$ are typed as [FONT=Courier New]( ), [ ], \{ \}. Note that a curly bracket must be preceded by a backslash. If you want larger delimiters, then you can use the [FONT=Courier New]\big, [FONT=Courier New]\Big, [FONT=Courier New]\bigg and [FONT=Courier New]\Bigg commands. For example​

​

[FONT=Courier New]xe^x = x \Big( \sum_{n=0}^\infty\frac{x^n}{n!} \Big)​

​

will give $$xe^x = x \Big( \sum_{n=0}^\infty\frac{x^n}{n!} \Big)$$ You can also let LaTeX choose the size of your delimiters. This can be done by typing \left or \right in front of the delimiter. For example​

​

[FONT=Courier New]xe^x = x \left( \sum_{n=0}^\infty\frac{x^n}{n!} \right)​

​

will give [tex]​

xe^x = x \left( \sum_{n=0}^\infty\frac{x^n}{n!} \right)​

[/tex] The size of the delimiters is determined by the size of what's between them. Because of this, there must be a [FONT=Courier New]\right for each [FONT=Courier New]\left and vice versa. So if you only want one of the delimiters to be displayed, you still have to tell LaTeX where the region that determines the size begins or ends, by typing "[FONT=Courier New]\left." or "[FONT=Courier New]\right." (i.e. you type a period instead of a delimiter), as in the following example.​

​

​

[FONT=Courier New]\left\{​

[FONT=Courier New]\begin{array}{l}​

[FONT=Courier New]x=r\cos\theta\\​

[FONT=Courier New]y=r\sin\theta​

[FONT=Courier New]\end{array}​

[FONT=Courier New]\right.​

[FONT=Courier New]~~\Rightarrow~~ x^2+y^2​

[FONT=Courier New]=r^2(\underbrace{\cos^2\theta+\sin^2\theta}_{=1})=r^2​

​

​

This gives [tex]​

\left\{\begin{array}{l}​

x=r\cos\theta\\​

y=r\sin\theta​

\end{array}\right.​

~~\Rightarrow~~ x^2+y^2​

=r^2(\underbrace{\cos^2\theta+\sin^2\theta}_{=1})=r^2​

[/tex] The array environment is explained in one of the documents linked to after the table of common symbols below.​

​

[B]Different fonts:[/B] Sometimes we wish to type things in a different font:​

​

​

[TR]
[TD][B]Name[/B][/TD]

[TD][B]Sample[/B][/TD]

[TD][B]LaTeX code[/B][/TD]
[/TR]
[TR]
[TD]Blackboard bold[/TD]

[TD]$\mathbb{ABCDE}$[/TD]

[TD][FONT=Courier New]\mathbb{ABCDE}[/TD]
[/TR]
[TR]
[TD]Calligraphic[/TD]

[TD]$\mathcal {ABCDE}$[/TD]

[TD][FONT=Courier New]\mathcal{ABCDE}[/TD]
[/TR]
[TR]
[TD]Fraktur[/TD]

[TD]$\mathfrak {ABCDE}$[/TD]

[TD][FONT=Courier New]\mathfrak{ABCDE}[/TD]
[/TR]
[TR]
[TD]Sans serif[/TD]

[TD]$\mathsf {ABCDE}$[/TD]

[TD][FONT=Courier New]\mathsf{ABCDE}[/TD]
[/TR]
[TR]
[TD]Roman (upright)[/TD]

[TD]$\mathrm {ABCDE}$[/TD]

[TD][FONT=Courier New]\mathrm{ABCDE}[/TD]
[/TR]
[TR]
[TD]Bold[/TD]

[TD]$\mathbf {ABCDE}$[/TD]

[TD][FONT=Courier New]\mathbf{ABCDE}[/TD]
[/TR]
[TR]
[TD]Typewriter[/TD]

[TD]$\mathtt {ABCDE}$[/TD]

[TD][FONT=Courier New]\mathtt{ABCDE}[/TD]
[/TR]

[td] [/td]

​

Note: The blackboard bold font only works with capital letters.​

​

​

[B]Frequently used symbols:[/B] This is a list of some of the most useful symbols and their LaTeX codes:​

​

​

[TR]
[TD][B]Name[/B][/TD]
[TD][B]Sample[/B][/TD]

[TD][B]LaTeX code[/B][/TD]
[/TR]
[TR]
[TD]Infinity[/TD]

[TD]$\infty$[/TD]

[TD][FONT=Courier New]\infty[/TD]
[/TR]
[TR]
[TD]Planck's constant[/TD]

[TD]$\hbar$[/TD]

[TD][FONT=Courier New]\hbar[/TD]
[/TR]
[TR]
[TD]Plus or minus[/TD]

[TD]$\pm,\mp$[/TD]

[TD][FONT=Courier New]\pm,\mp[/TD]
[/TR]
[TR]
[TD]Parallel[/TD]

[TD]$\parallel$[/TD]

[TD][FONT=Courier New]\parallel[/TD]
[/TR]
[TR]
[TD]Perpendicular[/TD]

[TD]$\perp$[/TD]

[TD][FONT=Courier New]\perp[/TD]
[/TR]
[TR]
[TD]For all[/TD]

[TD]$\forall$[/TD]

[TD][FONT=Courier New]\forall[/TD]
[/TR]
[TR]
[TD]There exists[/TD]

[TD]$\exists$[/TD]

[TD][FONT=Courier New]\exists[/TD]
[/TR]
[TR]
[TD]Ellipsis[/TD]

[TD]$\dots,\cdots,\vdots,\ddots$[/TD]

[TD][FONT=Courier New]\dots,\cdots,\vdots,\ddots[/TD]
[/TR]
[TR]
[TD]Arrows[/TD]

[TD]$\rightarrow,\leftarrow,\leftrightarrow$[/TD]

[TD][FONT=Courier New]\rightarrow,\leftarrow,\leftrightarrow[/TD]
[/TR]
[TR]
[TD][/TD]

[TD]$\Rightarrow,\Leftarrow,\Leftrightarrow$[/TD]

[TD][FONT=Courier New]\Rightarrow,\Leftarrow,\Leftrightarrow[/TD]
[/TR]
[TR]
[TD][/TD]

[TD]$\mapsto,\to$[/TD]

[TD][FONT=Courier New]\mapsto,\to[/TD]
[/TR]
[TR]
[TD][/TD]

[TD]$\uparrow,\downarrow$[/TD]

[TD][FONT=Courier New]\uparrow,\downarrow[/TD]
[/TR]
[TR]
[TD]Relations[/TD]

[TD]$\gt,\geq,\lt,\leq,\neq$[/TD]

[TD][FONT=Courier New]\gt,\geq,\lt,\leq,\neq[/TD]
[/TR]
[TR]
[TD][/TD]

[TD]$\gg,\ll,\equiv$[/TD]

[TD][FONT=Courier New]\gg,\ll,\equiv[/TD]
[/TR]
[TR]
[TD][/TD]

[TD]$\approx,\cong,\sim$[/TD]

[TD][FONT=Courier New]\approx,\cong,\sim[/TD]
[/TR]
[TR]
[TD]Super- & subscripts[/TD]

[TD]$x^n, x_n$[/TD]

[TD][FONT=Courier New]x^n, x_n[/TD]
[/TR]
[TR]
[TD]Tensor indices[/TD]

[TD]$R_{ab}{}^{cd}$[/TD]

[TD][FONT=Courier New]R_{ab}{}^{cd}[/TD]
[/TR]
[TR]
[TD]Fraction[/TD]

[TD]$\frac{ab}{cd}$[/TD]

[TD][FONT=Courier New]\frac{ab}{cd}[/TD]
[/TR]
[TR]
[TD]Roots[/TD]

[TD]$\sqrt{16},\sqrt[4]{16}$[/TD]

[TD][FONT=Courier New]\sqrt{16},\sqrt[4]{16}[/TD]
[/TR]
[TR]
[TD]Absolute value, norm[/TD]

[TD]$|x|,\|x\|$[/TD]

[TD][FONT=Courier New]|x|,\|x\|[/TD]
[/TR]
[TR]
[TD]Vectors, etc.[/TD]

[TD]$\vec r,\hat p, \tilde z$[/TD]

[TD][FONT=Courier New]\vec r,\hat p, \tilde z[/TD]
[/TR]
[TR]
[TD]Complex conjugate[/TD]

[TD]$z^*,\bar z,z^\dagger$[/TD]

[TD][FONT=Courier New]z^*,\bar z,z^\dagger[/TD]
[/TR]
[TR]
[TD]Primes[/TD]

[TD]$x', x''$[/TD]

[TD][FONT=Courier New]x', x''[/TD]
[/TR]
[TR]
[TD]Dirac notation[/TD]

[TD]$\langle \phi | \psi \rangle$[/TD]

[TD][FONT=Courier New]\langle \phi | \psi \rangle[/TD]
[/TR]
[TR]
[TD]Vector products[/TD]

[TD]$\vec A \cdot \vec B,\vec A \times \vec B$[/TD]

[TD][FONT=Courier New]\vec A \cdot \vec B,\vec A \times \vec B[/TD]
[/TR]
[TR]
[TD]Direct sum[/TD]

[TD]$V \oplus W$[/TD]

[TD][FONT=Courier New]V \oplus W[/TD]
[/TR]
[TR]
[TD]Tensor product[/TD]

[TD]$S \otimes T$[/TD]

[TD][FONT=Courier New]S \otimes T[/TD]
[/TR]
[TR]
[TD]Function composition[/TD]

[TD]$f \circ g$[/TD]

[TD][FONT=Courier New]f \circ g[/TD]
[/TR]
[TR]
[TD]Element of, not in[/TD]

[TD]$x \in A, x \not\in A$[/TD]

[TD][FONT=Courier New]x \in A, x \not\in A[/TD]
[/TR]
[TR]
[TD]Subset[/TD]

[TD]$A \subset B, B \subseteq C$[/TD]

[TD][FONT=Courier New]A \subset B, B \subseteq C[/TD]
[/TR]
[TR]
[TD]Set union, intersection[/TD]

[TD]$A \cup B, A \cap B$[/TD]

[TD][FONT=Courier New]A \cup B, A \cap B[/TD]
[/TR]
[TR]
[TD]Set subtraction[/TD]

[TD]$A \setminus B$[/TD]

[TD][FONT=Courier New]A \setminus B[/TD]
[/TR]
[TR]
[TD]Binomial coefficient[/TD]

[TD]$\binom{n}{k}, {_nC_r}$[/TD]

[TD][FONT=Courier New]\binom{n}{k}, {_nC_r}[/TD]
[/TR]
[TR]
[TD]Big stuff[/TD]

[TD]$$\bigcup_i A_i, \bigcap_i A_i$$[/TD]

[TD][FONT=Courier New]\bigcup_i A_i, \bigcap_i A_i[/TD]
[/TR]
[TR]
[TD][/TD]

[TD]$$\sum_{n=0}^\infty a_n x^n$$[/TD]

[TD][FONT=Courier New]\sum_{n=0}^\infty a_n x^n[/TD]
[/TR]
[TR]
[TD][/TD]

[TD]$$\prod_{n=0}^\infty a_n$$[/TD]

[TD][FONT=Courier New]\prod_{n=0}^\infty a_n[/TD]
[/TR]
[TR]
[TD]Derivatives[/TD]

[TD]$y', y'', y^{(n)}, \dot x, \ddot x$[/TD]

[TD][FONT=Courier New]y', y'', y^{(n)}, \dot x, \ddot x[/TD]
[/TR]
[TR]
[TD][/TD]

[TD]$\frac{df}{dx}, \frac{\partial f}{\partial x}$[/TD]

[TD][FONT=Courier New]\frac{df}{dx}, \frac{\partial f}{\partial x}[/TD]
[/TR]
[TR]
[TD][/TD]

[TD]$\nabla f, \nabla^2 \psi, \Box^2 \phi$[/TD]

[TD][FONT=Courier New]\nabla f, \nabla^2 \psi, \Box^2 \phi[/TD]
[/TR]
[TR]
[TD]Integrals[/TD]

[TD]$$\int e^x \, dx$$[/TD]

[TD][FONT=Courier New]\int e^x \, dx[/TD]
[/TR]
[TR]
[TD][/TD]

[TD]$$\oint \vec E \cdot d \vec A$$[/TD]

[TD][FONT=Courier New]\oint \vec E \cdot d \vec A[/TD]
[/TR]
[TR]
[TD][/TD]

[TD]$$\iint, \iiint$$[/TD]

[TD][FONT=Courier New]\iint, \iiint[/TD]
[/TR]
[TR]
[TD]Definite integrals[/TD]

[TD]$$\int_a^b e^x \, dx = \left. e^x \right|_a^b$$[/TD]

[TD][FONT=Courier New]\int_a^b e^x \, dx = \left. e^x \right|_a^b[/TD]
[/TR]
[TR]
[TD][/TD]

[TD]$$\int_{y=c}^d \int_{x=a}^b e^{x+y} \, dx \, dy$$[/TD]

[TD][FONT=Courier New]\int_{y=c}^d \int_{x=a}^b e^{x+y} \, dx \, dy[/TD]
[/TR]
[TR]
[TD]Trig functions[/TD]

[TD]$\sin x, \cos x, \tan x, \sec x, \csc x$[/TD]

[TD][FONT=Courier New]\sin x, \cos x, \tan x, \sec x, \csc x[/TD]
[/TR]
[TR]
[TD]Logarithms[/TD]

[TD]$\ln x, \log x, \log_2 64 = 6$[/TD]

[TD][FONT=Courier New]\ln x, \log x, \log_2 64 = 6[/TD]
[/TR]
[TR]
[TD]Hyperbolic trig[/TD]

[TD]$\sinh x, \cosh x, \tanh x$[/TD]

[TD][FONT=Courier New]\sinh x, \cosh x, \tanh x[/TD]
[/TR]

[td] [/td]

[td]​

​

Another nice list of frequently used symbols can be found [PLAIN]http://www.artofproblemsolving.com/Wiki/index.php/LaTeX:Symbols[/PLAIN] . http://amath.colorado.edu/documentation/LaTeX/Symbols.pdf PDF file contains another one. It also contains a brief explanation of the array environment, which was used in one of the examples above. If you don't see the symbol you need in any of these lists, try [URL='http://ctan.uib.no/info/symbols/comprehensive/symbols-a4.pdf']The comprehensive LaTeX symbol list[/URL] (also a PDF file).​

​

Sadly, not all LaTeX commands are being supported by MathJax. [PLAIN]http://www.mathjax.org/docs/1.1/tex.html#supported-latex-commands[/PLAIN] is the full list of supported commands.​

​

[B]Formulas that span multiple lines:[/B] Longer formulas and systems of equations can be typed using the align environment. An environment is a piece of code that begins with a [FONT=Courier New]\begin statement and ends with an [FONT=Courier New]\end statement. The align environment begins with \bеgin{align} and ends with \еnd{align}. Inside an align environment (and several other environments), the code [FONT=Courier New]\\ ends a line and starts a new one. The [FONT=Courier New]& symbol is used to indicate where rows are to be aligned, as in the following example.​

​

​

[FONT=Courier New]\begin{align}​

[FONT=Courier New](1+x)^n &\geq 1+nx\\​

[FONT=Courier New]&= \sqrt{(1+nx)^2}\\​

[FONT=Courier New]&= \sqrt{1+2nx+n^2x^2}​

[FONT=Courier New]\end{align}​

​

​

This yields [tex]​

\begin{align}​

(1+x)^n &\geq 1+nx\\​

&= \sqrt{(1+nx)^2}\\​

&= \sqrt{1+2nx+n^2x^2}​

\end{align}​

[/tex]​

Note: The [FONT=Courier New]\\ code only works in some environments.​

​

[B]Matrices:[/B] A matrix can easily be typed using the matrix, pmatrix, bmatrix or vmatrix environments. For example, the pmatrix environment starts with [FONT=Courier New]\bеgin{pmatrix} and ends with [FONT=Courier New]\еnd{pmatrix}. Columns are separated by [FONT=Courier New]& and rows are separated by [FONT=Courier New]\\ . Here is an example:​

​

​

[FONT=Courier New]\begin{pmatrix}​

[FONT=Courier New]1 & 2 & 3 & 4\\​

[FONT=Courier New]a & b & c & d\\​

[FONT=Courier New]x & y & z & w​

[FONT=Courier New]\end{pmatrix}​

​

​

This yields [tex]​

\begin{pmatrix}​

1 & 2 & 3 & 4\\​

a & b & c & d\\​

x & y & z & w​

\end{pmatrix}​

[/tex]​

The matrix, bmatrix and vmatrix environments produce similar results. Only the delimiters are different. See [PLAIN]http://www.math-linux.com/spip.php?article132[/PLAIN] for more examples.​

​

[B]The cases environment:[/B] Something like [tex]​

\begin{cases}​

2x+y+z & = 0\\​

3x+4y+5z & = 0\\​

x+2y+8z & = 0​

\end{cases}​

[/tex] can be easily typed using the cases environment. It starts with [FONT=Courier New]\bеgin{cases} and ends with [FONT=Courier New]\еnd{cases}. Rows must be separated by [FONT=Courier New]\\ and [FONT=Courier New]& is used to indicate where rows are to be aligned. The example above is produced by​

​

​

[FONT=Courier New]\begin{cases}​

[FONT=Courier New]2x+y+z & = 0\\​

[FONT=Courier New]3x+4y+5z & = 0\\​

[FONT=Courier New]x+2y+8z & = 0​

[FONT=Courier New]\end{cases}​

​

​

Another example is​

​

​

[FONT=Courier New]u(x) =​

[FONT=Courier New]\begin{cases}​

[FONT=Courier New]\exp{x} & \text{if } x \geq 0 \\​

[FONT=Courier New]1 & \text{if } x < 0​

[FONT=Courier New]\end{cases}​

​

​

which gives [tex]​

u(x) =​

\begin{cases}​

\exp{x} & \text{if } x \geq 0 \\​

1 & \text{if } x < 0​

\end{cases}​

[/tex] More information about cases, align and similar environments can be found [URL='http://en.wikibooks.org/wiki/LaTeX/Advanced_Mathematics']here[/URL].[/td]​

[td]Sandbox

If you wish to practice writing LaTeX or test some code, a sandbox is available [PLAIN]https://www.physicsforums.com/mathjax/test/preview.html[/PLAIN] . Please do not create threads just to practice LaTeX.​

Additional information

If you have questions, you can ask them in the [URL='https://www.physicsforums.com/forumdisplay.php?f=189']Math & Science Software subforum[/URL].​

​

If you go to advanced edit mode in one of the technical subforums (this doesn't work in the Forum Feedback & Announcements forum for example), you will see a button with a Σ symbol on it, above the input field. If you click on it, a menu with mathematical symbols will appear. When you select a symbol, its LaTeX code will be typed automatically, along with a pair of itex tags.​

​

A left-click on a LaTeX image will by default display a box with a larger version of the same image. Try it on this one: $$x_{j_{2^k}}$$ A right-click will display a menu where you can choose to​

[LIST]
[*]view the LaTeX source code.
[*]change the factor by which the larger image is larger than the default size.
[*]always scale all LaTeX images to a larger or smaller size.
[*]change the zoom trigger, i.e. change what you have to do to make the larger image appear.
[*]go to the MathJax help page.
[/LIST]​

If you change the zoom trigger to "hover", you will only have to hold the mouse pointer over the LaTeX image for the larger version to appear. However, this will also make it harder to right-click to bring up the menu, because a right-click on the larger image does nothing. So if you want to change it back, you have to be fast. Move the mouse pointer over the image, and right-click [I]before[/I] the larger image appears.​

​

Another way to see the LaTeX source code is of course to just click the QUOTE button next to the post. This is usually a better way, since it also shows the itex or tex tags, and the text around them, but it doesn't work in locked threads, or when the LaTeX image is in a quote box.​

Simple non-LaTeX options

If you just want a subscript or a superscript, you can use vBulletin's sub and sup tags. For example, [plain]x[sub]1[/sub][/plain] yields x[sub]1[/sub], and [plain]x[sup]2[/sup][/plain] yields x[sup]2[/sup]. If you don't want to type these tags, you can use the X[sub]2[/sub] and X[sup]2[/sup] buttons above the input field when you're in advanced edit mode.​

​

If you just want to insert a Greek letter or a mathematical symbol in your post, the easiest way is to just click on the symbol you want in the box of symbols to the right of the input field when you're in advanced edit mode. If you need a symbol that you don't see in that box, you can try to find it in [URL='https://www.physicsforums.com/showthread.php?p=4781371#post4845980']post #11[/URL], or on [PLAIN]http://tlt.its.psu.edu/suggestions/international/bylanguage/mathchart.html[/PLAIN] .​

​

Do not use these symbols, the sub/sup tags, or any other vBulletin tags inside a LaTeX ex-ression (i.e. between tex or itex tags).​

Acknowledgements

We are indebted to member and former admin chroot, whose efforts brought LaTeX to Physics Forums in the first place, and forum admin and owner Greg Bernhardt for updating to the currently-used MathJax processor. Numerous other members have provided valuable feedback and helped with the debugging process.​

​

The authors of this FAQ are​

[LIST]
[*]Fredrik
[*]micromass
[*]Redbelly98
[*]vela
[*]Mark44
[/LIST]​

[/td]

 

[micromass]

Why did nobody answer my post?

It happens quite a lot on this forum. Somebody posted a question and doesn't get answers. Or he does get answers but not the ones he anticipated. This is very unfortunate. This is why we have compiled a list of items to watch for improving your posts.

• Did you provide an attempt at solving the problem?
  This is perhaps the most common mistake that new members make. When posting homework, if you do not make any attempt yourself, then other people are not allowed to help at all! This holds particularly true in the homework forums!
  
  Of course, many people do not know where to begin, so how could they make an attempt? Well, an attempt could consist out of many things: check the theory in the textbook to see if there is something relevant, check previous problems to see if there is something you can use, draw a picture, try to find an intuitive answer by visualizing the problem, ... Here is a list of simple things you can try out when solving a problem: math.berkeley.edu/~gmelvin/polya.pdf This may not lead you to the answer, but it will make the problem clearer.
  
  Also, be sure to include all the relevant definitions. This is very helpful to us since sometimes there are multiple definitions for the same term. Telling us which definition you use gives us more information on how to give appropriate help. Also, you may want to think about how the definitions apply to your problem. (And be sure to tell us what you think!) For example, suppose you are given the problem
  
  

  Show that the cosine function is continuous.

  
  When posting this, you should at least include what the definition of continuous is. (Again, there are many possible definitions for continuous.) A definition of the cosine would also be quite helpful. Some properties that you might think are useful should also be given. Again, be sure to show us what you tried and where you're stuck. In showing that the cosine is continuous, you just need to show a definition. So tell us what is hard about it.
  
• But I looked at my problem for hours, and I really don't know how to start!
  If you truly looked at the problem for hours, then you must have something that you find confusing. This is something you should tell us about, and it shows you thought about your problem. Also, when we ask for attempts, people often think that we already want half the solution. This is not true. Attempts consists out of many different forms. You could include a specific question that's confusing you, an approach that doesn't seem to work, definitions or theorems that you're having problems with applying, a previous problem that seems to ask something related but that is easier, etc.
  
  
• Did you follow the homework template?
  When posting in the homework forums, you are required to follow the homework template. This look like this:
  
  
  
  The requirement to follow the homework template is not just us trying to bully you; it does have a good reason. It makes the problem much clearer to the homework helpers, and perhaps also to you. It is never a bad idea to structure your posts, and our template helps you with this. Also, under "relevant equations", you should also post the definitions of the terms you're using. See the above question.
  
  
• Did you post that your homework is due in a few hours and that you need help NOW?
  If you did, then you should remove this. It doesn't get you a faster response. Some people even refuse to help posters who post things like "ASAP", "Help needed fast", etc. Also, if your homework is due in a few hours, then perhaps you should have asked help on it earlier. People here are volunteers and are not paid to help you. We will answer when we can, but it's not nice to put us under pressure.
  
  
• Did you research the problem first yourself?
  Often we get questions like
  
  

  Hey, can anybody explain what the theory of relativity says?

  
  Such a threads get very little answers because the question is far too broad, and because it is apparent that the poster did not look for answers himself. This blog post by ZapperZ gives more explanation about this: https://www.physicsforums.com/blog.php?b=3588
  
  
• Did you give enough explanation in your post?
  It is always better to give too much information to us than too little. First, try to define the terms and the variables you use. For example
  
  

  How do you prove if $\Phi:A\rightarrow B$ is injective?

  
  is bad because you never defined $\Phi$, A, or B. This is without doubt an exaggerated example, but do define all variables you use. Similarly:
  
  

  How do I know if $\{1,2,3\}$ is Lindelof?

  
  Not many people know what Lindelof is, even if they studied the relevant subject. Those people could answer you if you explained that term, but now they are probably not going to bother. So do explain the terms you are using.
  Of course, it would be silly to explain terms like force or derivative. These terms are well-known. So it requires a bit of skill to see which terms to define or not. But if you didn't receive a good answer yet, then perhaps a follow-up post to explain some terms is needed!
  
  
• Did you explain your education level and the relevant courses you are taking?
  Usually, we can deduce the level of education from the post, but this is not always possible. It may very well happen that some people start talking over your head or start saying things that are obvious to you. The more general your question is, the more important it is to include some personal information about yourself. Also, if you know the answer to a problem, it helps to give that too!
  
• Did you give a link to a book you are reading?
  Looking up the relevant page in google books and giving us the link helps us quite a lot. Of course, the entire book is often not available online, so it might be impossible for you to give this link. In that case, do quote the exact problem or paragraph you want to discuss. In any case, tell us the book you're using and the page. There might be some people owning the book you do.
  
  
• Did you use LaTeX?
  Reading plain computer symbols is often very annoying to helpers. And when there is not a nice enough lay-out, many people will ignore your post. This can be easily solved by taking out some time to learn about LaTeX. It really isn't hard to learn, and you would make the job for us much easier!
  A tutorial on LaTeX can be found here: https://www.physicsforums.com/showthread.php?p=3977517&posted=1#post3977517
  
  If you don't want to learn LaTeX for some reason, then at least use the x₂ and x² buttons to make subscripts and supscripts. Also try to use the symbol list to the right of the posting window to make the post more readable.
  
  
• Did you post your question as an attachment? Is it written by hand?
  Writing your question down on a piece of paper and then posting it as an attachment is quite convenient for you, but it is not convenient for the people who are trying to help you. Some will ignore such posts. And if the handwriting is not easy to read, they will certainly ignore it.
  
  
• Did you include a descriptive title?
  A title like "help needed" doesn't tell the helpers much. It is obvious that help is needed, otherwise you wouldn't post a thread. If you include a descriptive title, then perhaps you will get more people to read your thread!
  
  
• How long did you wait for a reply?
  It can sometimes take quite long before you get a good reply. This may be, for example, because you are posting in a different time zone than most members. Always wait at least 24 hours before bumping a post. (And even then, please bump only once!) Be aware: bumping your thread is often counterproductive. Many helpers will give preference to posts without any replies. If they see a reply in your post, they will often assume that somebody else is already dealing with the problem!
  Also, if you make a mistake in your post, it is much better to edit your post than to reply to your thread. Again, posts with replies tend to get fewer answers than posts without replies!

The authors of this FAQ were:

• Fredrik
• micromass
• tiny-tim
• vela

 

[micromass]

Suggestions in Forum feedback
We of course welcome new suggestions to improve the quality of PF. But there are some suggestions that we truly get quite a lot. Please read the following points first before making a suggestion. If you still feel that your idea has merit, then you can post it.

• We should add a like button.
  This is not going to happen for now, for several reasons:
  • We do not have the capability at the moment. That is, the forum software does not allow such a feature.
  • We feel that a like button is a dangerous thing. It may be that posts that get liked are simply not very good. The fact that many people like a post does not mean that the information is correct or scientific. We give out Homework Helper/Science Advisor medals precisely to reward the people who constantly make high quality posts and who have a good attitude. These medals should make the readers alert that the information is (most likely) of high accuracy. A like button does not imply high accuracy.
  • If you wish to thank somebody who helped you, you can always post a small "thank you" in the thread or in his visitor messages.
• Can we add a new forum for xyz?
  Before posting a request to add a new forum, please read the following post by ZapperZ (to be found in this thread https://www.physicsforums.com/showthread.php?t=554734):
  

  We frequently get such question on why such-and-such does not have a forum to itself.
  
  Let's me give you this fact for you to consider. Condensed matter physics is the LARGEST sub-division in physics, and in fact, can easily be argued as the largest subtopic in physics. Still, do you see a forum solely dedicated to this subject area? Go take a look around. It shares the subforum with Atomic/molecular physics, and computational physics! Imagine that! Even a subject area that is the LARGEST in the field of physics does not have a forum all to itself!
  
  So already, the argument of importance, of significance, and of size has no bearing on a subject matter getting its own forum. What is more important are (i) frequency of the topic being posted (ii) the level of SUSTAINED interest in that topic (iii) the number of regular members participating in that topic. It is of no point to create a forum for a topic just because ... There has to be an online demand for it in this forum that can justify such a creation.
  
  So forget what you think about the subject matter in general. Do you think your topic qualifies in all the 3 criteria to justify the creation of its own forum? Do you think the posting frequency matches that of, say, the posting frequency in the Relativity forum?

  So, if you can demonstrate that (i), (ii) and (iii) are satisfied, then we will take your request for a new forum under consideration.
• Can we have a forum for speculative posts/original research?
  This is not going to happen. We had such a forum for many years, but we decided to remove it. The decision was based on the fact that such a forum attracts crackpottery and does not meet the mission of PF. Indeed, our mission is to promote standard, mainstream science.
  If you do wish to discuss speculative ideas or original research, then you will find many forums on the internet that allow you to do so.
  
  Also see: https://www.physicsforums.com/blog.php?b=2979
• Can we add a feature that indicates when a certain question is "solved"?
  We had such a feature in the past, but for some reason it stopped working. Bringing this feature back is now impossible because there are many technical difficulties.

 

[micromass]

Known bugs and features

NOTE: This post is now obsolete, after the upgrade to PF 4.0. We'll update it with the new, improved bugs after the transition settles down!

• I have made several posts but my post counter does not increase.
  This is because you have posted in the lounge. Posts there do not count towards your total posts. Only posts in the technical forums count. So it is entirely possible to make several posts and still have a post counter of 0.
• My avatar and my signature won't show up.
  Only PF contributors can have an avatar and a signature. You can become a contributor either by making a donation to our forum: https://www.physicsforums.com/payments.php or by posting a PF flyer at your university: https://www.physicsforums.com/showthread.php?t=338366
  Furthermore, Homework Helpers and Science Advisors also are allowed to have an avatar and a signature.
• I have unsubscribed from threads but I still receive e-mails from PF.
  Unsubscribing from e-mails is indeed not so easy here. Here is what you need to do to not receive any more e-mails:
  
  1) Go to "My PF", then to "Edit Options". In the tab "Messaging & Notifications", you should see "Default Thread Subscription Mode". You should change this to "No email notification".
  However, this will stop the emails from all future threads. Emails from threads that you are already subscribed on are not going to be stopped. In order to change this, do the following:
  
  2) Go to "My PF" and then to "List Subscriptions". You should then see a list of all threads you are subscribed to and whether or not you get an email notification. You can now remove subscription from these threads manually by highlighting these threads and by changing the subscription type to "no notification" (at the bottom).
• When making a thread in the homework forums, the homework template shows up multiple times.
  This is a known bug. Every time you preview your thread, an extra homework template gets added to your post. It's perfectly ok to delete this extra template.

 

[vela]

How to Ask for Homework Help

When you open a new homework thread, you are asking volunteers to spend their time to help you, so spend a little of your time to make their job easier. Effective communication is the key, so keep these general considerations in mind when you make a new thread:

• We're not in your class; we don't know what's in your notes; we don't know what you've tried; and we can't read your mind. All we have to go on is what you write.
• We don't really know you. If it's not obvious from the question, let us know your level of knowledge so that we can reply on an appropriate level.

The guidelines below will help you avoid some common obstacles to getting help. (Many of the points are, in fact, part of the forum rules, and as such, they're not really suggestions or advice. You're supposed to be following them already!)

1. Use the homework template.
   This is primarily to make your post clearer to the homework helpers, but it's also there to help you. It is never a bad idea to structure your work (here and in general), and sometimes organizing your thoughts can help you clear up your confusion on your own. Also, if you don't have enough to fill out the template, it's a sign you shouldn't be posting yet.
2. Reproduce the problem statement accurately.
   It's very frustrating trying to help a student with a problem only to discover that he or she omitted important information.
   
   Ideally, type the problem statement exactly as worded. You're probably not the best arbiter of what's important and what's not, so include everything. If you decide to paraphrase or summarize anyway, make sure you're not accidentally changing the meaning or omitting important information. If you're only asking about one part of a long problem, it may not be necessary to type up the entire problem, but you need to ensure you've provided the proper context for the sub-problem.
3. Show us that you've thought about the problem.
   The forum rules require that you show an attempt at solving the problem on your own. Obviously, one reason we want to see your work is because we prefer to help those who are genuinely trying and interested in learning. What's more important is that we need to see what you've tried so we know how to help you. For your attempt, you can offer a partial solution to the problem, but you don't always have to. What we're really interested in is seeing what you're thinking so we can identify and clear up any misconceptions or points of confusion.
   
   Here are some common mistakes to avoid:
   • Don't simply say "I have no clue," "I have no idea where to start," or "I'm completely lost." These don't qualify as attempts. Instead, it suggests you haven't put much effort into reading and understanding your textbook and lecture notes, going over similar examples, etc. The helpers aren't here to answer your questions so you don't have to read your book.
   • Don't simply say "I tried for hours and didn't get anywhere." This is really no better than saying "I have no clue." It tells us absolutely nothing about where you're getting stuck. If you tried for hours, you must have had some thoughts about the problem. What were they? Show us what you tried, explain why you think it was wrong, and so on. Better yet, identify what's confusing you and ask specific questions to help you figure things out.
   • Don't just give a vague or general description of what you tried. If the problem lies in the execution, as it often does, we can't help you find mistakes without seeing your work in detail. Even if you provide your final result, it usually does little to help us figure out where your attempt went awry.
4. Do not simply post images of the problem statement or your work.
   While posting images may be convenient for you, it's actually one of the most effective ways of getting your request for help ignored. Images are often too big, too small, rotated, upside down, out of focus, dimly lit, or of otherwise poor quality, and your handwriting probably isn't as easy to read as you think it is. Images are a hindrance to the helpers as portions of the problem statement or your work can't easily be quoted. Using images also doesn't qualify as filling out the homework template, so your post may be deleted.
   
   So type up the problem statement and your work. Think "If I can't be bothered to spend my time typing it, why should they be bothered to spend their time reading it?" Use scans or photos for supporting figures. You may, of course, attach an image of the problem statement in addition to the typed version; in fact, if it's a complicated or long problem, you probably should. But you should always provide a typed version as well.
   
   When you do use an image to your post, make sure it's in focus, oriented the right way, well lit, etc. It seems like this should be obvious, but experience has shown that people frequently post incredibly poor images. Add it as an attachment to the post. Don't host it externally. That way it will remain on PF indefinitely, and your thread will remain useful to future visitors.
5. Format your post to make it easy to read and follow.
   You're more likely to get responses if prospective helpers don't have to decipher what you wrote.
   
   Use paragraphs and separate them with blank lines. Take advantage of the typesetting features in vBulletin. Use LaTeX for mathematics. There's a good tutorial on LaTeX here.
   
   Follow standard conventions when writing mathematical expressions. In particular, use parentheses where necessary. Don't make us have to guess what you really meant to say.
   
   Don't use large, bold, or colored type to draw attention to your question. We can read the normal font just fine.
6. Use proper English.
   Grammatical and spelling errors littering a post can be quite distracting and make it hard to read, and in the worst case, these errors can obscure the meaning of what you wanted to say. You're more likely to get responses when your post is well written.
   
   Use proper grammatical structure, punctuation, capitalization, and spelling to express your ideas as clearly as possible and to maintain the quality of the posts on the forum. In particular, avoid the use of txt-speak, which many of us find grating. Physics Forums isn't your cell phone.
7. Proofread.
   Despite your best efforts, a few mistakes may slip through — a typo here, a missing tag there. It never hurts to check over what you wrote for errors and to fix them. It's a good habit to get into in general.
   
   Preview your post before submitting it. Find obvious errors and fix them.
   
   After you submit your post, reread it one more time in its entirety to see it makes sense as a whole, especially if you did a lot of editing while composing your post. Make sure it looks the way you expect. Fix broken tags, broken links, etc. Delete extra copies of the template.
   
   If you find mistakes, click on the Edit button which appears in the bottom right corner of your post. The ability to edit a post is temporary, so don't put it off. Avoid replying to your own post with corrections because some helpers will skip over your thread when it looks like someone has already replied.

 

[jtbell]

About PF’s Policy on Speculative Discussions

• Why doesn't Physics Forums allow people to post "new theories" and other speculative ideas, or try to disprove well-established theories like relativity?
  
  We believe such discussions detract from our mission of helping people who want to understand science as practiced by professional scientists, as described in our Global Guidelines. We have chosen to focus on these people, rather than on those who want freewheeling speculation. There are other places on the internet that cater to such speculation.
  
  One of our major "markets" is high-school and university students who use us to help them understand the material that they are studying. We don't want to give them a mistaken impression of the current "state of the art" in professional science by encouraging excessive speculation, cranks and crackpots.
• But isn't speculation an important part of the scientific process?
  
  Yes, indeed! It's so important that we think it should be left to the professionals, at graduate-school level and beyond. Before one can productively think "outside the box", one has to know where the walls of the box are in the first place. Professional scientists already have ways of discussing their ideas with colleagues. We do not aim to become one of those ways. It is not part of our mission to aid in the advancement of science, only in the understanding of science.
• What about people who do have professional-level knowledge of physics, maybe even with a Ph.D., but aren't affiliated with a university or other institute? Shouldn't they have a place to discuss their ideas with others?
  
  We tried to cater to people like these, with a moderated Independent Research forum. It failed. See below for a history of this attempt.
• What if a well-established physicist wanted to post his new theory here and discuss it before publishing it?
  
  We would politely explain our policy and tell him that he is very welcome to discuss his theory here after publishing it.
• What about students who come up with tentative theories as part of their learning process?
  
  Some students try to post such theories as a way of filling the gaps in their current understanding of science, with the intention of learning from having them shot down. We think it is more effective to pose focused questions about current theories, to address those gaps.
• Has PF at least tried allowing speculative discussions?
  
  Yes, we did, during our earlier years. People spent a lot of time arguing with crackpots and others who didn't want to give up their ideas even in the face of experimental evidence.
  
  Sometime in 2003 or earlier, we created a Theory Development forum and moved all speculative threads there. This allowed such discussions to continue, while keeping the other forums focused on mainstream science.
  
  After a while, we decided that the Theory Development forum wasted too much of our and other posters' resources in arguing with crackpots and cranks, and in moderating threads that got out of control, and that it detracted from our main mission. In July 2005, we closed Theory Development and replaced it with a moderated Independent Research forum:
  
  https://www.physicsforums.com/showthread.php?t=81172
  
  (The forum was originally going to be named Outside the Mainstream, but it was changed to Independent Research just before its actual startup.) Briefly, new threads had to start with an opening post similar to the abstract of a scientific journal article, and meet certain standards to help screen out obvious crackpot-type stuff. If the opening post was approved, discussion would proceed normally. The intent was to allow discussion of serious alternative theories and speculations that don't contradict well-established science.
  
  It turned out that very few opening posts made it through the initial moderation process. The ones that did, tended either to produce little actual discussion, or to degenerate into a sort of "blog" containing only posts from the original poster, adding to his ideas or revising them. In June 2011, we decided that the Independent Research forum was not productive enough to be worth the time and effort needed to moderate it, and so we closed it:
  
  https://www.physicsforums.com/showthread.php?t=506643
  
  Since then, we have allowed only discussion of theories that are already "out there" and being discussed in mainstream professional circles.
• Further reading
  
  For one [now emeritus] Mentor's thoughts on this topic, see this post written by ZapperZ:
  
  https://www.physicsforums.com/showthread.php?t=765736
  
  (It was written before we closed the Independent Research forum.)
  

Authors and contributors to this FAQ:

• jtbell
• DaleSpam
• participants in many discussions of this topic in Forum Feedback & Announcements

 

[micromass]

Some information about physicsforums and its history

Summary
Owner Greg Bernhardt started Physics Forums as a high school extra credit project for a physics class in 2001.

Some number crunching
Technicals:
Owner: Greg Bernhardt
Greg's real job: Web Design/Development
PF DOB: 2001
Organization: Undefined, Bernhardt Media LLC.
Revenue: Adsense, Gold Memberships
PF Data Size: ~6gigs
Location: Datacenter in Dallas
Monthly Costs: high $XXX
Software: vBulletin

Demographics:
PF average 100,000+ visitors, 100+ new members and 1000+ posts per day.

80% search engines, 10% referral sites, 10% direct traffic

80% of our visitors are from North America. 10% Europe, 5% asia and 5% other.

55% use Internet Explorer. 38% use FireFox. 5% Safari, 1% Opera

70% on high speed internet, 10% dialup

88% on Windows, 8% Mac, 3% Linux

History of the forums

PF is a beautiful example of people coming together to create something with the purpose to help, to learn, and to create a sense of community among people that share a love of science and not for monetary gain. - Evo

The Beginning (Spring 2001)
It comes to many peoples surprise to find I am actually not very good at math and physics. PF started in spring of 2001. I was taking Physics II in high school my senior year. The semester was ending and I found myself getting a "D" in the class. I badly needed at least a "C" to minimize impact on my overall GPA.

Through the year I gained mass interest in the Internet, web designing and community building. My interest in physics was also sparked by popular physics books by Michio Kaku, Brian Greene, Stephen Hawking's and Paul Davies.

So I thought of proposing the idea of creating a useful physics community on the web as an extra credit project to my physics teacher. The teacher bought it and away I went. In the end it took me just a month to get enough done and promote it for the thing to look half way decent. I found a "C" on my report card end of semester :)

Early Years (2001-2003)
PF started out on the ASP driven software of Snitz. I believe we also started on the web host "DreamHost". Unfortunately two years later in 2003 we grew too big and too fast. We ended up having to ditch the software and the host. This resulted in starting completely from scratch. The database had about 200,000 posts in it. It still hurts to lose all that data to this day. But it has proven to be a turning point marker for PF's history. We moved to a dedicated server and professional software to last us for many years. During this time I also admit hiring some non qualified staff members. Once we got Integral, Tom Mattson and chroot, things started to change.

The Middle Ages (2003-2005)
Before the "beginning from scratch", PF was becoming quite popular, but our forum management and organization was severely lacking. Over the next couple of years PF would prove itself a giant in the science web community. Early 2004 we even hosted Michio Kaku's official forums.

In these years PF would:
1. Develop an organized forum structure
2. Start creating a strict but fair policy
3. Hire competent staff with similar visions
4. Start member award days
5. Install LaTeX for equations
6. Start the Homework Helper and Science Advisor programs

The "Golden" Years (2005-Present)
Physics Forums is now finally working like a well oiled high performance machine. The standard has been set. We're pretty much coasting now that we have a complete system in place that has proven to be successful. Crackpots and spam are almost non-existent. Along with what seemed like a new design a year, we found one that works and will stick with for a long time now.

A few highlights of these past couple years include:
1. Partnership with Scientific American
2. Partnership with PhD Comics
3. PF Library

Bigger and better things planned for the future!

List of mentors
Let's use this section to list Mentors. Oldest to Newest. (Bold means they are still on staff)

1. Monique (Niqqie,theOwl)
2. JordanW
3. Silverquest
4. Phobos
5. Grady
6. dav2008
7. MacCoder
8. joaoninhio
9. Beatle42
10. SCOTT2004
11. Sting1983 (Sting)
12. Stephen
13. Integral
14. Zero
15. Kerrie (skorpiano)
16. BryanGmyrek
15. Tom Mattson (Tom)
16. Janus
17. ahrkron
18. damgo (alis)
19. selfAdjoint
20. chroot
21. Hurkyl
22. Russ Watters
23. Engima
24. Another God
25. HallsofIvy
26. Ivan Seeking
27. dduardo
28. Doc Al
29. Iansmith
30. hypnagogue
31. Evo
32. Gokul43201
33. ZapperZ
34. loseyourname
35. Moonbear
36. SpaceTiger
37. Berkeman
38. jtbell
39. vanesch
40. Pervect
41. Math is Hard
42. Astronuc
43. cristo
44. George Jones
45. Hootenanny
46. Kurdt
47. Redbelly98
48. Vanadium_50
49. D H
50. Borek
51. bcrowell
52. Mark44
53. Ryan_m_b
54. micromass
55. vela
56. lisab
57. cepheid
58. Dalespam
59. Fredrik
60. SammyS
61. mfb
62. Office_Shredder
63. gneill
64. SteamKing
65. Drakkith
66. Chestermiller
67. Nugatory

 

[micromass]

Physicsforums medals and guru's

Physics Forums awards various types of medals to members for showing ability or dedication in a given area. These different awards are described below.

There are several different medals or rankings a member can achieve while being an active part of Physics Forums. Each medal has different requirements that must be fulfilled. The different medals/"rankings" a member can have on PF are:

Normal Member: This is not very hard to achieve. It involves signing up for free. Do it today!

PF Contributor Medal: These members are also known as "Gold Members" due to their names being displayed in Gold in the forums. In order to obtain this medal a member must contribute a donation that goes towards running the site. If you enjoy PF and wish to contribute, you may do so by clicking the "Upgrade" button on the top of the page. Other benefits these members get (along with the medal and gold name) include:

No ads
Set invisible ability
Custom title
Ability to have a Signature
Avatars
Profile photo
200pm limit
Ability to view who's online
User notes
Boolean searching

Homework Helper Medal: This is the first of the PF merit-awarded medals discussed here. As such it entails responsibility beyond that of the average poster. In order to be recognized as a Homework Helper a member must:

1) Give correct and reliable help to students in the homework help forums of the site.

2) Help in the homework forums regularly whenever they are able.

3) Be a regular and "established" member of PF. (By this I mean they must show that their contributions will most likely continue in the future. i.e. They are members who are not as likely to disappear on a whim and never help again.)

Members are nominated by current homework helpers and mentors. The medals are then awarded by the administrator, Greg Bernhardt. Due to the amount of effort homework helpers devote to keeping the homework sections of PF running smoothly and efficiently, they are listed under the "Staff" link at the top of any PF page along with Science Advisors, Mentors, and Administrators. Homework helpers also from time to time participate in policy/structure discussions.

List of homework helpers can be found here.
Science Advisor Medal: The science advisor medal is a merit awarded medal as well. As such, it entails responsibility beyond that of the average poster. In order to be considered for a science advisor medal a member must:

1)Offer reliably correct explanations for scientific questions posed in the various forums of PF. Science Advisor medals are awarded to those members who have demonstrated an unmistakable expertise in a certain field of science discussed on PF.

2)Help other members understand their field of expertise a little better through their postings.

3) Be a regular and "established" member of PF. (Same meaning as above.)

Members are nominated by current science advisors and mentors. The medals are then awarded by the administrator, Greg Bernhardt. Due to the amount of effort science advisors devote to keeping high quality scientific discussions on PF, they are listed under the "Staff" link at the top of any PF page along with Homework Helpers, Mentors, and Administrators. Science Advisors also from time to time participate in policy/structure discussions.

List of science advisors can be found here.

Guru Plaque: Every year, around December, PF members (of any level) vote for members who have been nominated by mentors for excelling in different areas. The winner of the poll for each category receives the "Guru" plaque for that category. They will keep the plaque until next year when the voting begins again. Guru plaques are awarded every year in the following categories:

Physics
Astronomy/Cosmology
Mathematics
Engineering
Technology
Other Sciences
Homework Helping
Community Spirit
Newcomer
Funniest Member

Mentor Rank: A PF mentor is a member who has been chosen by current mentors and administrators because of their demonstration of unparalleled commitment to PF, extensive scientific knowledge in a certain field, and perceived ability to be able to effectively moderate discussions on PF and run the day to day operations of the community. The mentors help maintain the high-quality scientific discussion that makes PF famous! Many of the mentors are professional scientists and graduate students. Mentors are distinguished by a green name in their posts on the forums and a "PF Mentor" label underneath their name. The Physics Forums mentors are listed under the "Staff" at the top of any PF page.

List of current mentors can be found here.

Retired Staff Medal
This medal simply denotes past service as a Mentor or Admin.

Administrator Rank: The administrators (Greg Bernhardt, Astronuc, and Borek) keep the site running by looking after the technical end of things. Greg also owns Physics Forums. Administrators are distinguished by a blue name in their posts on the forums and a "PF Admin" label underneath their name.

List of administrators can be found here.

Current Gurus

Physics:
PeterDonis

Mathematics:
HallsOfIvy

Astro/Cosmo:
marcus

Engineering:
AlephZero

Other Sciences:
Ygggdrasil

Homework Help:
Simon Bridge
haruspex

Community Spirit:
WannabeNewton

Best Humor:
Enigman

Newcomer:
R136a1

Guru Roll of Honour

This list recognises those users who have previously been voted Gurus. We congratulate them on their achievement and thank them for their contributions to the community.

Physics
2003: marcus
2004: ZapperZ
2005: marlon
2006: pervect
2007: George Jones
2008: mgb_phys
2009: DrChinese
2010: DrChinese
2011: Fredrik
2012: Dalespam
2013: PeterDonis[/color]

Astronomy & Cosmology
2003: schwarzchildradius
2004: Chronos
2005: SpaceTiger
2006: hellfire
2007: Marcus
2008: Marcus
2009: Marcus
2010: Marcus
2011: Marcus
2012: bcrowell
2013: Marcus[/color]

Mathematics
2003: Mathman
2004: Matt Grime
2005: Matt Grime
2006: mathwonk
2007: Matt Grime
2008: mathwonk
2009: Dick
2010: mathwonk
2011: mathwonk
2012: AlephZero
2013: HallsOfIvy[/color]

Engineering
2004: Clausius
2005: Astronuc
2006: FredGarvin
2007: FredGarvin
2008: FredGarvin
2009: Mgb_phys
2010: vk6kro
2011: AlephZero
2012: jim hardy
2013: AlephZero[/color]

Nuclear Engineering
2012: tsutsuji

Chemistry¹
2004: chem_tr
2005: GCT

Biology¹
2004: Moonbear
2005: DocToxyn

Other Sciences³
2003: FZ+
2006: Bystander
2007: Chemisttree
2008: Andre
2009: Borek
2010: Andy Resnick
2011: Andy Resnick
2012: Chemisttree
2012: Ygggdrasil[/color]

Technology⁶
2004: graphic7
2005: franznietzsche
2007: -Job-

Homework Helper
2005: Tide
2006: OlderDan
2007: Dick
2008: tiny-tim, Dick
2009: tiny-tim
2010: tiny-tim, Mark44
2011: I Like Serena, tiny-tim
2012: ehild, Dick
2013: Simon Bridge, haruspex[/color]

Community Spirit
2003: drag
2004: Gokul43201
2005: Math is Hard
2006: Astronuc
2007: Gokul43201
2008: Redbelly98
2009: Lisab
2010: Lisab
2011: Gad
2012: Pengwuino
2013: WannabeNewton[/color]

Newcomer
2009: Twofish-Quant
2010: Char. Limit
2011: A. Neumaier
2012: mfb
2013: R136a1[/color]

Best Humour⁴
2003: Mr. Robin Parsons
2004: Tribdog
2005: Danger
2006: Pengwuino & Cyrusabdollahi (Joint)
2007: Wolram
2008: Borek
2009: DaveC426913
2010: Danger
2011: Pengwuino
2012: OmCheeto
2013: Enigman[/color]

Philosophy²
2003: Boulderhead
2004: Les Sleeth
2005: Les Sleeth

Crackpot of the Year⁵
2003: LogicalAthiest

Best Thread of the Year⁵
2003: Astronomy

(1) From 2006 onwards, the Biology and Chemistry categories have been merged into a single category.
(2) After 2005 the Philosophy Guru was phased out.
(3) Formerly 'Biology & Chemistry'.
(4) Formerly 'Funniest Member'.
(5) Phased out after 2003.
(6) Merged with 'Other Sciences' in 2008

 

[Redbelly98]

Copy-and-paste math symbols

Originally posted as a blog entry on Sep7-08 by Redbelly98

As a simple, but limited, alternative to LaTeX, some symbols are also standard ascii characters. To use them, simply copy-and-paste from here into your own post.
.

Symbols viewable to everybody:α β γ δ ε ζ η θ ι κ λ μ ν ξ ο π ρ ς σ τ υ φ χ ψ ω . . . . . Γ Δ Θ Λ Ξ Π Σ Φ Ψ Ω

∂ ∫ ∏ ∑ . . . . . ← → ↓ ↑ ↔ . . . . . ± − · × ÷ √ . . . . . ¼ ½ ¾ ⅛ ⅜ ⅝ ⅞

∞ ° ² ³ ⁿ Å . . . . . ~ ≈ ≠ ≡ ≤ ≥ « » . . . . . † ‼Bold, Times New Roman font (some symbols look better that way):

α . ← . [FONT=Times New Roman][B]α[/B]
γ . ← . [FONT=Times New Roman][B]γ[/B]
ν . ← . [FONT=Times New Roman][B]ν[/B]
π . ← . [FONT=Times New Roman][B]π[/B]
χ . ← . [FONT=Times New Roman][B]χ[/B]
ψ . ← . [FONT=Times New Roman][B]ψ[/B]
Π . ← . [FONT=Times New Roman][B]Π[/B]
Φ . ← . [FONT=Times New Roman][B]Φ[/B]
Ψ . ← . [FONT=Times New Roman][B]Ψ[/B]Popular combinations, grouped together for convenient copy-and-paste:

→∞ . . ±√ . . θ = ° . . ∂² . . ω² . . (x-μ)²/2σ² . . ω=2πν . . λν . .2π/λ . . μΩ . .

1/4πε_o . ← . 1/4[FONT=Times New Roman][B]πε[/B][sub]o[/sub]

χ² . ← . [FONT=Times New Roman][B]χ[/B]²

A^† . ← . A[SUP]†[/SUP]

_____________________________​

Not viewable to all users (please try to avoid these unless absolutely necessary):

∇ ⋅ ∗ ∝ ∠ ∧ ∴ ∼ ≅ ∃ ℏ . . . . . ↵ ⇐ ⇑ ⇒ ⇓ ⇔

 

[Borek]

1/4πε_o . ← . 1/4[FONT=Times New Roman][B]πε[/B][sub]o[/sub]

Alternatively fractions can be formatted as

¹/₄πε_o . ← . [sup]1[/sup]/[sub]4[/sub][FONT=Times New Roman][B]πε[/B][sub]o[/sub]