# Latex question, new line

by Redbelly98
Tags: latex, line
 Mentor P: 11,911 I can't seem to generate multiple lines within a single [ tex ][ /tex ] block. It's supposed to happen if I type \\ but it just never works for me. Example: $$f_1(x) = x \\ f_2(x) = 1-x^2$$ The "f2(x)" is supposed to start on a new line. What am I doing wrong?
P: 364
 Quote by Redbelly98 I can't seem to generate multiple lines within a single [ tex ][ /tex ] block. It's supposed to happen if I type \\ but it just never works for me. Example: $$f_1(x) = x \\ f_2(x) = 1-x^2$$ The "f2(x)" is supposed to start on a new line. What am I doing wrong?
Unfortunately I'm not going to be of any help to you. I've also tried this numerous times, but to the same effect.
 PF Patron Sci Advisor Emeritus P: 9,789 I don't think that the \\ has ever worked on the forums, it must be some kind of bug in the software. However, one can start new lines using the flalign environment. \begin{flalign*} f_1\left(x\right) & = & & x\\ f_2\left(x\right) & = & & 1-x^2\\ f_3\left(x\right) & = & & \frac{f_1}{f_2} \\ & = & & \frac{x}{1-x^2} \end{flalign*} And the code: \begin{flalign*} f_1\left(x\right) & = & & x\\ f_2\left(x\right) & = & & 1-x^2\\ f_3\left(x\right) & = & & \frac{f_1}{f_2} \\ & = & & \frac{x}{1-x^2} \end{flalign*} The * is used to suppress line enumeration. The alignment of each element is fixed to alternate between left and right as shown below \begin{flalign*} right & left & right & ... \\ right & left & right & ... \\ right & left & right & ... \\ \end{flalign*} But you can add additional & separators to obtain the desired layout, as I have done above: \begin{flalign*} right & left & & left \\ right & left & & left \\ right & left & & left \\ \end{flalign*} I agree that this method is far more verbose than simply using \\ is mathmode, but it is the only work-a-round that i know of for PF. Note that the eqnarray environment does not display correctly either at PF.
Mentor
P: 11,911

## Latex question, new line

Thanks Hoot. So the &'s help line up the equal signs. And if I just wanted to left-justify each line, each line would start with a &.

      \begin{flalign*}
& f_1(x) = x \\
& f_2(x) = 1-x^2
\end{flalign*}
I also found this previous discussion in a locked thread:
http://www.physicsforums.com/showthr...x+line&page=19

However, in chroot's examples the code uses TWO begin and TWO end statements, eg.
\begin{equation*}
\begin{split}

So the single begin statement
\begin{flalign*}
is an improvement over that.

Thanks again!

RB
PF Patron
Emeritus
P: 16,094
 Quote by Hootenanny II don't think that the \\ has ever worked on the forums
I've never known it to work in LaTeX either. (Remember that [ itex ] ... [/itex] is analogous to $...$, and [ tex ] ... [/tex] is analogous to $...$)
PF Patron
 Quote by Hurkyl I've never known it to work in LaTeX either. (Remember that [ itex ] ... [/itex] is analogous to $...$, and [ tex ] ... [/tex] is analogous to $...$)
 PF Patron HW Helper Sci Advisor P: 4,084 $$\] This is the first line.\\ This is the second line.\\ This is the third line. $E=mc^2$ This is another line. $$$ Click on the rendered image to see what I did. Maybe some $$\LaTeX$$ expert can explain what is going on. I suspect that the forum software already places us in a $$\LaTeX$$ environment... and these \[$ break us out of it somehow.
 Quote by robphy I suspect that the forum software already places us in a $$\LaTeX$$ environment... and these  break us out of it somehow.
Sounds precisely right to me: the $$tag acts like $and by typing$, you close the latex environment.  Mentor P: 11,911 Now that we are using MathJax, I am revisiting how to generate multiple lines within a single LaTeX code block. EDIT: Nevermind, I found out how to do this: http://www.physicsforums.com/showthread.php?p=261329 Also, scroll down post #1 here for multi-line examples: http://www.physicsforums.com/showthread.php?t=8997 Please disregard the following... I just now noticed a problem with these old posts (for example Post #'s 1 and 3 above). Right now I see the LaTeX code, without the [_tex_] tags, enclosed in a box and left-right centered in the page. I have FireFox 4 and Windows 7. Apparently MathJax doesn't like the double-backslash newline indicator, and that is preventing the code from being processed properly. Testing: Using same code from Post #1 again: [tex] f_1(x) = x \\ f_2(x) = 1-x^2$$ Same code, with double-backslash removed: $$f_1(x) = x f_2(x) = 1-x^2$$ So the question is, is it possible anymore to generate a new line within the same [_tex_] code block? Hootenanny's trick in Post #3 used to work -- not that I am advocating going back to the old LaTeX system.
 PF Patron Sci Advisor Emeritus P: 16,094 Here: \begin{align} a & b \\ c & d \end{align} This one gives weird results: $$\begin{multline} a b \\ c d \end{multline}$$