I'd like to number multiline equations and reference them, à la MathJax's Align and Gather environments. Can this be accomplished? If so, how?


2 Answers 2


In the align environment, I use \tag to number. \label is also supported by MathJax. \ref can be used to reference a line using \label and \tag.

For example: $$ \int_{-\infty}^\infty e^{-\pi x^2}\,\mathrm{d}x=1\label{a}\tag{1} $$ and reference it here: $\ref{a}$

  • $\begingroup$ Thank you. Why is it that when I use \label in the align environment, the equations don't display but rather the underlying mathjax code? $\endgroup$
    – Evan Aad
    Commented Apr 8, 2014 at 21:32
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    $\begingroup$ @EvanAad: There seems to be a problem when editing. I find that when I save the edit and reload the page, things look okay. The same thing happened while I was editing my answer. $\endgroup$
    – robjohn Mod
    Commented Apr 8, 2014 at 21:33
  • 1
    $\begingroup$ See this post for some details about why that is the case. Also, see the SOUP script for workarounds to this and many other small issues . $\endgroup$ Commented Apr 8, 2014 at 23:05
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    $\begingroup$ But how was this done? I can't edit this answer, so I can't see the source code. $\endgroup$ Commented Dec 2, 2017 at 15:11
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    $\begingroup$ @DanielMartin: I think that even if you can't edit an answer, you can right-click on a MathJax rendered formula and a pop-up will appear allowing you to choose "Show Math As > TeX Commands". $\endgroup$
    – robjohn Mod
    Commented Dec 2, 2017 at 15:27
  • $\begingroup$ In the displayed equation you use \tag{1}. To refer to it you use \ref{a}. How does this work? I am not able to refer to \tagged equations. Am I missing the relevant part of MathJaX code? $\endgroup$
    – wdacda
    Commented Oct 5, 2020 at 5:45
  • $\begingroup$ @wdacda: The \label{a} is what is referenced by the \ref{a} which is displayed as $\ref{a}$. $\endgroup$
    – robjohn Mod
    Commented Oct 5, 2020 at 6:13
  • $\begingroup$ @robjohn I get it now! With \tag{1} we control what will show as the "name" of the equation. We need the label to use it in \ref. Wonderful! I was quite slow. But better ever, then never. I prefer using \eqref, it is more like in math texts. Thank you! $\endgroup$
    – wdacda
    Commented Oct 5, 2020 at 7:01

In order to see the tags during edit, the following trick can be used.

$$ \begin{aligned} a & = b & (1) \\ c & = d & (2) \end{aligned} $$

But now the equations cannot be hyperlinked to.


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