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Physics Forums FAQ and HowTo

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Blog Entries: 8
Recognitions:
Gold Member
Staff Emeritus
How to make a post at physicsforums

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 http://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 "NEW REPLY" 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: http://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:

Code:
[b]1. The problem statement, all variables and given/known data[/b]

[b]2. Relevant equations[/b]

[b]3. The attempt at a solution[/b]
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 this blog post by Redbelly98, or on this web page.

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 $...$ tags.

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:

Code:
[B][/B]
Typing between these tags will yield bolded text. For example:

Code:
This is [B]bold[/B] text.
will result in:

This is bold text.

 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:

Code:
This is [I]italic[/I] 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:

Code:
This is [U]underlined[/U] 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:

Code:
x[SUB]2[/SUB] and a[SUP]2[/SUP].
will give

x2 and a2.

Do not use this in combination with $...$.

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:

Code:
[SPOILER]Highlight me to see me![/SPOILER]
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

Code:
[STRIKE]This is wrong[/STRIKE] This is right.
will give

This is wrong 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 [*] with then the text. For example:

Code:
[LIST=1]
[*] First item.
[*] Second item.
[/LIST]
will give
1. First item.
2. Second item.

While,

Code:
[LIST]
[*] First item.
[*] Second item.
[/LIST]
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

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

Code:
This is normal.
[INDENT]This is indented[/INDENT]
[INDENT][INDENT]This is indented twice[/INDENT][/INDENT]
gives

This is normal.
This is indented
This is indented twice
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:

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

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

Code:
[YOUTUBE]dQw4w9WgXcQ[/YOUTUBE]
gives

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 [IMG]...[/IMG] 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.

Code:
[CODE]This is between code tags[/CODE]
yields

Code:
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
• Fredrik
• jtbell
• micromass
• Redbelly98
• tiny-tim
Attached Thumbnails

 Blog Entries: 8 Recognitions: Gold Member Science Advisor Staff Emeritus How to type mathematical equations here? 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 Code: $y = a x^2 + bx + c$ the result will be $y = a x^2 + bx + c$. Alternatively, you can type LaTeX code between [tеx] and [/tеx]. 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 Code: $$\Delta \theta = \omega_0 t + \frac{1}{2} \alpha t^2.$$ the result will be $$\Delta \theta = \omega_0 t + \frac{1}{2} \alpha t^2.$$ For the ones already familiar with LaTeX: itex tags are analogous to $, and tex tags are analogous to $$. The easiest way to learn LaTeX is to see what others have done. If you see a post with a nice equation in it, just click QUOTE (at the bottom of the post) to see what the author did. Simplified tags: Instead of typing [itеx] and [/itеx], you can type ## and ##. Instead of typing [tеx] and [/tеx], you can type$$ and $$. For example Code: The equation ##x+2=3## implies$$x=1.$$ Will yield: The equation ##x+2=3## implies$$x=1.$$Punctuation: If you're using tex tags and you want a comma or a period after your formula, you should put it before the closing tex tag. If you're using itex tags, it doesn't matter if you put it before or after the closing itex tag. Also, when you use tex tags, the software will put a blank line before and after the formula. So you don't have to type any line breaks before the opening tex tag or after the closing tex tag. However, you can type a single line break before a tex tag without changing the output. The following example illustrates these ideas. Code: Let $f:\mathbb R\rightarrow\mathbb R$ be the function defined by $$f(x)=x^2,$$ for all $x\in\mathbb R$. Let $f:\mathbb R\rightarrow\mathbb R$ be the function defined by $$f(x)=x^2,$$ for all $x\in\mathbb R$. Important bug: vBulletin (the forum software) has a feature that will sometimes break correct LaTeX code. If you type more than 50 characters without a space, vBulletin will insert one for you after the 50th character. This will break the code unless you're lucky enough to have the space end up before a LaTeX command rather than in the middle of it. To prevent this from happening, you will have to make sure that your code contains a space at least once every 50 characters. If you often write long pieces of LaTeX code, you may want to start to routinely type extra spaces that will be ignored by the LaTeX processor, for example before equality signs and LaTeX commands that aren't arguments of other LaTeX commands. Another bug is that if you edit a post that contains LaTeX code without going to advanced edit mode, the code will not be parsed when you view the thread immediately after saving the changes. The math looks fine to everyone else, but you will need to refresh the page (in your browser) to see the math again. A very short introduction to LaTeXThe previous section explains how to include LaTeX code in posts, but it doesn't explain LaTeX. So in this section, we will explain how to type common mathematical formulas in LaTeX. Special characters: The following characters have a special meaning in LaTeX: #$ % { } _ ^ \ ~ So if you want one of these characters to be displayed, you must type the code for the symbol rather than the symbol itself. The LaTeX codes for the first six of these symbols are: \# \\$ \% \{ \} \_ Spacing: LaTeX ignores most of the spaces and end-of-line characters you type. For example Code: $$x y z$$ will produce $$x y z$$ There is a number of LaTeX commands that you can use to control the horizontal distance between characters. \ (followed by a space) or ~ inserts a space. The difference is that ~ ensures that LaTeX will not break the line at that space. \, inserts a small space. \! inserts a small negative space (moves the cursor a little to the left). \quad and \qquad insert larger spaces. You can also use the \hspace command to explicitly specify the width of the space. For example, Code: $$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$$ To get the result $f(x)=1\ \text{if} \ x>0$, you can't just type Code: $f(x)=1 if x>0$ The result will be ugly: $f(x)=1 if x>0$. Any of these codes will do a better job: Code: $f(x)=1\ \text{if}\ x>0$ $f(x)=1~\text{if}~x>0$ $f(x)=1\text{ if }x>0$ These are the results: $f(x)=1\ \text{if}\ x>0$ $f(x)=1~\text{if}~x>0$ $f(x)=1\text{ if }x>0$ The \text command tells LaTeX to interpret what comes next as text, instead of as variables. Subscripts and superscripts: To put a subscript on a variable, use the _ symbol. To put a superscript on a variable, use the ^ symbol. For example, if you type Code: $x_y,\ x^y$ the result is $x_y,\ x^y$. If you want to display just the subscript or the superscript, and not the variable, type {} where the variable would normally be. This trick is also useful when the horizontal positioning of the indices is important, as in the following example. Code: $$\Lambda^\mu_\nu,\ \Lambda_\nu^\mu,\ \Lambda^\mu{}_\nu,\ \Lambda_\nu{}^\mu$$ $$\Lambda^\mu_\nu,\ \Lambda_\nu^\mu,\ \Lambda^\mu{}_\nu,\ \Lambda_\nu{}^\mu$$ Subscripts and superscripts work with integrals, limits, summations, and several other symbols. For example, Code: $$\lim_{n\rightarrow +\infty} {\frac{\sin(x)}{x}}$$ will give us $$\lim_{n\rightarrow +\infty} {\frac{\sin(x)}{x}}$$ If you do the same thing between itex tags, then you get $\lim_{n\rightarrow +\infty} {\frac{\sin(x)}{x}}$. The subscript is written next to the limit instead of beneath it. If you don't like this, you can use the \displaystyle command. For example, Code: $\displaystyle\lim_{n\rightarrow +\infty} {\frac{\sin(x)}{x}}$ will give $\displaystyle\lim_{n\rightarrow +\infty} {\frac{\sin(x)}{x}}$. Grouping: By default, most LaTeX commands act only on the first character or command on its right. (\displaystyle is one of the exceptions). To make them act on longer pieces of input, use curly brackets { }. For example Code: $x^{10}+x^10$ gives $x^{10}+x^10$. If you want to limit the scope of a \displaystyle command, place the curly brackets as in this example Code: $\lim_n x_n={\displaystyle\lim_n x_n}=\lim_n x_n$ The result is $\lim_n x_n={\displaystyle\lim_n x_n}=\lim_n x_n$. You can nest brackets within brackets as deeply as you want to build up a complicated expression. For example Code: $\sqrt{1+\sqrt{1+\sqrt{1+x}}}$ gives $\sqrt{1+\sqrt{1+\sqrt{1+x}}}$. Delimiters: The delimiters $(~),[~], \{~\}$ are typed as ( ), [ ], \{ \}. Note that a curly bracket must be preceded by a backslash. If you want larger delimiters, then you can use the \big, \Big, \bigg and \Bigg commands. For example Code: $$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)$$ You can also let LaTeX choose the size of your delimiters. This can be done by typing \left or \right in front of the delimiter. For example Code: $$xe^x = x \left( \sum_{n=0}^\infty\frac{x^n}{n!} \right)$$ will give $$xe^x = x \left( \sum_{n=0}^\infty\frac{x^n}{n!} \right)$$ The size of the delimiters is determined by the size of what's between them. Because of this, there must be a \right for each \left and vice versa. So if you only want one of the delimiters to be displayed, you still have to tell LaTeX where the region that determines the size begins or ends, by typing "\left." or "\right." (i.e. you type a period instead of a delimiter), as in the following example. Code: $$\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$$ $$\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$$ The array environment is explained in one of the documents linked to after the table of common symbols below. Different fonts: Sometimes we wish to type things in a different font. For example Blackboard bold, Calligraphic, Fraktur, Sans serif, Roman (upright), bold and typewriter. \begin{align} &\mathbb{ABCDEFGHIJKLMNOPQRSTUVWXYZ}\\ &\mathcal{ABCDEFGHIJKLMNOPQRSTUVWXYZ}\\ &\mathfrak{ABCDEFGHIJKLMNOPQRSTUVWXYZ}\\ &\mathsf{ABCDEFGHIJKLMNOPQRSTUVWXYZ}\\ &\mathrm{ABCDEFGHIJKLMNOPQRSTUVWXYZ}\\ &\mathbf{ABCDEFGHIJKLMNOPQRSTUVWXYZ}\\ &\mathtt{ABCDEFGHIJKLMNOPQRSTUVWXYZ} \end{align} The codes Code: $\mathbb A$ $\mathcal A$ $\mathfrak A$ $\mathsf A$ $\mathrm A$ $\mathbf A$ $\mathtt A$ give the results $\mathbb A$, $\mathcal A$, $\mathfrak A$, $\mathsf A$, $\mathrm A$, $\mathbf A$ and $\mathtt A$ respectively. Note: The blackboard bold font only works with capital letters. Frequently used symbols: This is a list of some of the most useful symbols and their LaTeX codes: $$\begin{array}{l|c|c} \hline \text{Infinity} & \text{\infty} & \infty \\ \text{Reduced Planck's Constant} & \text{\hbar} & \hbar \\ \text{Plus-minus} & \text{\pm, \mp} & \pm, \mp \\ \text{Parallel} & \text{\parallel} & \parallel \\ \text{Perpendicular} & \text{\perp} & \perp \\ \text{For all} & \text{\forall} & \forall \\ \text{There exists} & \text{\exists} & \exists \\ \text{Ellipsis} & \text{\cdots, \vdots, \ddots, \dots} & \cdots, \vdots, \ddots, \dots \\ \hline \text{Arrows} & \text{\rightarrow, \leftarrow, \leftrightarrow} & \rightarrow, \leftarrow, \leftrightarrow \\ & \text{\Rightarrow, \Leftarrow, \Leftrightarrow} & \Rightarrow, \Leftarrow, \Leftrightarrow \\ & \text{\mapsto, \to} & \mapsto, \to \\ & \text{\uparrow, \downarrow} & \uparrow, \downarrow \\ \hline \text{Relations} & \text{\geq, \leq, \neq} & \geq, \leq, \neq \\ & \text{\gg, \ll, \equiv} & \gg, \ll, \equiv \\ & \text{\approx, \cong, \sim} & \approx, \cong, \sim \\ \hline \text{Superscript} & \text{x^n} & x^n \\ \text{Subscript} & \text{x_i} & x_i \\ \text{Tensor indices} & \text{R_{ab}{}^{cd}} & R_{ab}{}^{cd} \\ \text{Fraction} & \text{\frac{1}{2}} & \frac{1}{2} \\ \text{Square root} & \text{\sqrt{16}} & \sqrt{16} \\ \text{Nth root} & \text{\sqrt[4]{16}} & \sqrt[4]{16} \\ \text{Absolute value} & \text{|x|} & |x| \\ \text{Norm} & \text{\|\vec{x}\|} & \|\vec{x}\| \\ \text{Accents} & \text{\hat{p}, \vec{r}, \tilde{z}} & \hat{p}, \vec{r}, \tilde{z} \\ \text{Complex conjugate} & \text{z^*, \bar{z}, z^\dagger} & z^*, \bar{z}, z^\dagger \\ \text{Dirac notation} & \text{\langle \phi | \psi \rangle} & \langle \phi | \psi \rangle \\ \text{Multiplication} & \text{A \cdot B, A \times B} & A\cdot B, A\times B \\ \text{Direct Sum} & \text{V \oplus W} & V \oplus W \\ \text{Tensor Product} & \text{S \otimes T} & S \otimes T \\ \text{Function composition} & \text{f \circ g} & f\circ g \\ \text{Element of} & \text{x \in A} & x \in A \\ \text{Not in} & \text{x \not\in A} & x \not\in A \\ \text{Subset} & \text{A \subset B, B \subseteq C} & A \subset B, B \subseteq C \\ \text{Set Union} & \text{A \cup B} & A \cup B \\ \text{Set Intersection} & \text{A \cap B} & A \cap B \\ \text{Set Subtraction} & \text{A \setminus B} & A \setminus B \\ \hline \text{Binomial coefficient} & \text{\binom{n}{k}, {_nC_r}} & \binom{n}{k}, {_nC_r} \\ \hline \text{Big stuff} & \text{\bigcup_i A_i} & \bigcup_i A_i \\ & \text{\bigcap_i A_i} & \bigcap_i A_i \\ & \text{\sum_{n=0}^\infty a_n x^n} & \sum_{n=0}^\infty a_n x^n \\ & \text{\prod_{n=0}^\infty a_n} & \prod_{n=0}^\infty a_n \\ \hline \text{Derivatives} & \text{y', y'', y^{(n)}} & y', y'', y^{(n)} \\ & \text{\dot{x}, \ddot{x}} & \dot{x}, \ddot{x} \\ & \text{\frac{\partial f}{\partial x}} & \frac{\partial f}{\partial x} \\ & \text{\nabla f} & \nabla f\\ & \text{\Box^2 \phi} & \Box^2 \phi \\ \hline \text{Integrals} & \text{\int e^x\,dx} & \int e^x\,dx \\ & \text{\oint \vec{E}\cdot d\vec{A}} & \oint \vec{E}\cdot d\vec{A} \\ & \text{\iint, \iiint} & \iint, \iiint \\ \hline \text{Elementary Functions} & \text{\sin x, \cos x, \log (x+y), ...} & \sin x, \cos x, \log(x+y), \dots \\ \hline \end{array}$$ Another nice list of frequently used symbols can be found here. This PDF file contains another one. It also contains a brief explanation of the array environment, which was used in one of the examples above. If you don't see the symbol you need in any of these lists, try The comprehensive LaTeX symbol list (also a PDF file). Sadly, not all LaTeX commands are being supported by MathJax. This is the full list of supported commands. Formulas that span multiple lines: Longer formulas and systems of equations can be typed using the align environment. An environment is a piece of code that begins with a \begin statement and ends with an \end statement. The align environment begins with \bеgin{align} and ends with \еnd{align}. Inside an align environment (and several other environments), the code \\ ends a line and starts a new one. The & symbol is used to indicate where rows are to be aligned, as in the following example. Code: \begin{align} (1+x)^n &\geq 1+nx\\ &= \sqrt{(1+nx)^2}\\ &= \sqrt{1+2nx+n^2x^2} \end{align} This yields \begin{align} (1+x)^n &\geq 1+nx\\ &= \sqrt{(1+nx)^2}\\ &= \sqrt{1+2nx+n^2x^2} \end{align} Note: The \\ code only works in some environments. Matrices: A matrix can easily be typed using the matrix, pmatrix, bmatrix or vmatrix environments. For example, the pmatrix environment is started with \bеgin{pmatrix} and ended with \еnd{pmatrix}. Columns are separated by & and rows are separated by \\ . Here is an example: Code: $$\begin{pmatrix} 1 & 2 & 3 & 4\\ a & b & c & d\\ x & y & z & w \end{pmatrix}$$ This yields $$\begin{pmatrix} 1 & 2 & 3 & 4\\ a & b & c & d\\ x & y & z & w \end{pmatrix}$$ The matrix, bmatrix and vmatrix environments produce similar results. Only the delimiters are different. See this web page for more examples. The cases environment: Something like $$\begin{cases} 2x+y+z & = 0\\ 3x+4y+5z & = 0\\ x+2y+8z & = 0 \end{cases}$$ can be easily typed using the cases environment. It is started with \bеgin{cases} and ended with \еnd{cases}. Rows must be separated by \\ and & is used to indicate where rows are to be aligned. The example above is produced by Code: $$\begin{cases} 2x+y+z & = 0\\ 3x+4y+5z & = 0\\ x+2y+8z & = 0 \end{cases}$$ Another example is Code: $$u(x) = \begin{cases} \exp{x} & \text{if } x \geq 0 \\ 1 & \text{if } x < 0 \end{cases}$$ which gives $$u(x) = \begin{cases} \exp{x} & \text{if } x \geq 0 \\ 1 & \text{if } x < 0 \end{cases}$$ More information about cases, align and similar environments can be found here. SandboxIf you wish to practice writing LaTeX or test some code, a sandbox is available here. Please do not create threads just to practice LaTeX. Additional information If you have questions, you can ask them in the Math & Science Software subforum. If you go to advanced edit mode in one of the technical subforums (this doesn't work in the Forum Feedback & Announcements forum for example), you will see a button with a Σ symbol on it, above the input field. If you click on it, a menu with mathematical symbols will appear. When you select a symbol, its LaTeX code will be typed automatically, along with a pair of itex tags. A left-click on a LaTeX image will by default display a box with a larger version of the same image. Try it on this one: $$x_{j_{2^k}}$$ A right-click will display a menu where you can choose toview 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. 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 before 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, x[sub]1[/sub] yields x1, and x[sup]2[/sup] yields x2. If you don't want to type these tags, you can use the X2 and X2 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 this blog post by Redbelly98, or on this web page. Do not use these symbols, the sub/sup tags, or any other vBulletin tags in LaTeX mode (i.e. between tex or itex tags). AcknowledgementsWe 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 Fredrik micromass Redbelly98 vela

Blog Entries: 8
Recognitions:
Gold Member
Staff Emeritus

Physics Forums FAQ and HowTo

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:

Code:
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution
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: http://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: http://www.physicsforums.com/showthr...=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
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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?
 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: http://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.