Troubleshooting Latex: Can't Generate Multiple Lines in a Single [tex] Block?

[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:

$$f_1(x) = x \\ <br /> f_2(x) = 1-x^2$$

The "f₂(x)" is supposed to start on a new line.

What am I doing wrong?

 

[phyzmatix]

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:

$$f_1(x) = x \\ <br /> f_2(x) = 1-x^2$$

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.

 

[Hootenanny]

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.

$$\begin{flalign*}<br /> f_1\left(x\right) & = & & x\\<br /> f_2\left(x\right) & = & & 1-x^2\\<br /> f_3\left(x\right) & = & & \frac{f_1}{f_2} \\<br /> & = & & \frac{x}{1-x^2}<br /> \end{flalign*}$$

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.

 

[Redbelly98]

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:
https://www.physicsforums.com/showthread.php?t=8997&highlight=latex+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

 

[Hurkyl]

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 \[ ... \])

 

[Hootenanny]

I've never known it to work in LaTeX either. (Remember that [ itex ] ... [/itex] is analogous to $ ... $, and [ tex ] ... [/tex] is analogous to \[ ... \])

Hmm, you're quite right: \\ only works in array enviroments in LaTeX

 

[robphy]

$$\]<br /> This is the first line.\\<br /> This is the second line.\\<br /> This is the third line.<br /> \[<br /> E=mc^2<br /> \]<br /> This is another line.<br /> \[$$

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.

 

[cristo]

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.$$

 

[Redbelly98]

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: https://www.physicsforums.com/showthread.php?p=261329

Also, scroll down post #1 here for multi-line examples: https://www.physicsforums.com/showthread.php?t=8997

Please disregard the following...[/color]

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:
$$f_1(x) = x \\ <br /> f_2(x) = 1-x^2$$

Same code, with double-backslash removed:
$$f_1(x) = x <br /> f_2(x) = 1-x^2$$

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.

 

[Hurkyl]

Here:
$$\begin{align}<br /> a & b \\<br /> c & d<br /> \end{align}$$

This one gives weird results:
$$\begin{multline}<br /> a b \\<br /> c d<br /> \end{multline}$$