## LaTeX forum ⇒ Math & Science ⇒ Equation Alignment causes several Errors

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Wenneguen
Posts: 4
Joined: Sun Jan 20, 2013 8:58 pm

### Equation Alignment causes several Errors

Hello,

LaTeX tells me there are 12 errors in there :
\begin{aligned}   $|a_n| \sim |b_n| &\iff |a_n| - |b_n| = o(|a_n|) \\&\iff \forall \varepsilon > 0, \exists N \in \mathbb{N}, \forall n \ge N, |a_n| - |b_n| \le \varepsilon |a_n|$\end{aligned}

I guess it is because of the stuff in the aligned environment, since it is the first time I use it. Could someone explain how to use it so that LaTeX does not detect errors ? (surprisingly LaTeX displays exactly what I want to make, but I like documents without errors :D)

Thank you ! :)
Last edited by localghost on Sun Jan 20, 2013 10:06 pm, edited 1 time in total.
Reason: Longer passages of source code are tagged as code block, not as in-line code.

localghost
Site Moderator
Posts: 9206
Joined: Fri Feb 02, 2007 12:06 pm
Location: Braunschweig, Germany
Please always provide a self-contained and minimal example to make a problem comprehensible at all. This would also prevent others from guesswork and random shots.

The aligned environment only works in math mode, either in-line or display mode. Since you didn't provide a full example, one can only guess that you are perhaps looking for something like this.
\documentclass[11pt]{article}\usepackage[T1]{fontenc}\usepackage{mathtools}  % loads »amsmath« \begin{document}   \begin{equation}     \begin{aligned}       |a_n| \sim |b_n| &\iff |a_n| - |b_n| = o(| :D a_n|) \\       &\iff \forall \varepsilon > 0, \exists N \in \mathbb{N}, \forall n \ge N, |a_n|-|b_n| \le \varepsilon |a_n|     \end{aligned}   \end{equation}\end{document}

And it's not necessary to activate in-line math mode ($…$) inside another math environment.

Best regards and welcome to the board
Thorsten
LaTeX Community Moderator

¹ System: openSUSE 13.1 (Linux 3.11.10), TeX Live 2013 (vanilla), TeXworks 0.5 (r1351)
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