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I have a single equation that is 3 pages long. I'm currently using a split environment to format the equation. However, the equation will not separate into different pages, and after I fill up the first page it overruns it.

I understand that the \displaybreak command will not work in the split environment, so I was wondering how else I could be displaying the equation. I figure I could use multline, but I wanted to have alignment in the equation.

Mico
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Asking
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    Do you HAVE to write it as a single equation instead of, say, a=b+c+d\b=...\c=...\d=... ? – John Kormylo Dec 23 '17 at 15:11
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    Did you put \allowdisplaybreaks? Are you aware of this post? –  Dec 23 '17 at 15:17
  • @JohnKormylo Yeah, unfortunately. – Asking Dec 23 '17 at 15:22
  • @marmot I have the split environment, I can't use \displaybreaks – Asking Dec 23 '17 at 15:23
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    What about the align*, gather*, multline*… environment? \displaybreaks works fine with them. Especially the align* environment can be used as a substitute for a combination of equation* and split if necessary. – Franck Pastor Dec 23 '17 at 15:30
  • I still need to have the equation numbered, though. – Asking Dec 23 '17 at 15:36
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    Use align and add \notag to everything not numbered. – John Kormylo Dec 23 '17 at 15:40
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    Use equation and, inside equation, use aligned. It will save you typing \notag for three pages. – Bernard Dec 23 '17 at 15:55
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    @Bernard He can't use aligned, since the contents of this environment can't be split between two pages. Same for split, gathered and alignedat. – Franck Pastor Dec 23 '17 at 16:42
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    @Asking: Please provide some more specifics regarding your expected output: (1) You want the equation number. Okay. On which of the 3 pages? One of them, or all of them? (2) What do you have surrounding the equation (before and after)? (3) Can you mock up an example of your current setup as a minimal example? – Werner Dec 23 '17 at 17:31
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    Off-topic: Are you sure your readers will appreciate, let alone be impressed by, the fact that you've mastered the (highly overrated) skill of typesetting a single equation that spans three full pages? Or will their eyes glaze over quickly and will they simply stop taking in anything at all? Is this an article intended for publication in a journal? If so, don't be surprised if the editors balk and make you rewrite major portions (if they don't reject the piece right off the bat). – Mico Dec 23 '17 at 21:43
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    My first impression is that you should rewrite the equation so that it doesn't take up three pages.... Without seeing the equation it is not clear how to do this but I'd be surprised if you can't take out common "important" parts of the equation and give them names so as to shorten the equation and make it more digestible. –  Dec 23 '17 at 23:24

1 Answers1

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Assuming you really can't re-organize the math material and hence are forced to display a single equation which (a) spans 3 pages and (b) takes a single equation number, I suggest you proceed as follows:

  • Use an align* environment, not a nested equation/split environment.

  • Provide the instruction \allowdisplaybreaks to, you guessed it, allow page breaks in a long display-math environment.

  • Use a \tag directive to place the equation number in a suitable location. Assuming this equation number should be 1 larger than the preceding equation number, use a \refstepcounter{equation} instruction as well.

The following code is (hopefully) suggestive of how you may wish to proceed.

\documentclass{article}
\usepackage{amsmath} % for 'align*' env. and `\tag` macro
\allowdisplaybreaks  % allow page breaks in display-math material

\newcommand\showeqnum{% % handy macro to increment eq. num and display it
     \refstepcounter{equation}
     \tag{\theequation}}

\begin{document}

\begin{align*}
A 
&= B \\
&= C \\
&= D \\
&= E \\
&= F \\
&= G \\
&= H \showeqnum \label{eq:3pager}
\end{align*}

A cross-reference to equation \eqref{eq:3pager}.
\end{document}
Mico
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