Is it possible to pagebreak aligned equations?

Question

The report I'm writting features a lot of long, multiple lines equations. To reduce visual polution I've been using an aligned environment nested inside equation. This way (unlike just using an align environment) I get only a single label for all the lines.

The problem is that so many long equations often need to be broken into two pages, otherwise I get lots of blank vertical space in the document. However the aligned environment does not allow the \displaybreak command.

Is there an alternative way to achieve a pagebreak inside an aligned equation?

Here's a sample ofthe equations I'm using

\begin{equation}
    \begin{aligned}
    ...\\
    ...\\  %I need to pagebreak here
    ...\\
\end{aligned}\end{equation}    

Answer 1

In relation to the comments I want to answer this question.

First of all to allow page breaks inside equations you have to set the command \allowdisplaybreaks. Without setting this one no page break occurs.

Using a simple align-environment. Of course as @DavidCarlisle suggested you can use the star variant to suppress the numbering and set a specific tag by \tag.

The environment split can't handle page breaks.

\documentclass{article}
\usepackage{amsmath}
\usepackage{kantlipsum}
\usepackage{showframe}
\allowdisplaybreaks

\begin{document}
\kant[1-3]
\begin{align*}
    a\\
    b\\
    c\\
    d\\
    e\tag{\stepcounter{equation}\theequation}\\
    f\\
    g\\
    h\\
    i
\end{align*}
\end{document}

Answer 2

Additionally to the above answers, as asked in comments, the command \allowdisplaybreaks from amsmath can be used locally do a display break by using the \begingroup and \endgroup commands:

\begingroup
\allowdisplaybreaks
\begin{align}
    ....
\end{align}
\endgroup

Or simpler syntax (shoutout to GWPR):

{\allowdisplaybreaks
\begin{align}
    ....
\end{align}
}

Answer 3

Just add the \allowdisplaybreaks command from the amsmath package to the preamble of your document. Works only with the math environments provided by this package. So you can use align.

Answer 4

I am posting my version because it took me some time to figure that out and i hope it will help others also.

\allowdisplaybreaks goes before \begin{document} and it is used only once. Then a very general code example for an equation is the following

\begin{align} 
\sum{...a very large expression...} &= \sum{...another large expression...} \nonumber \\ 
&= \sum{...a result which is also large but needs to be aligned under first "="...} \nonumber \\
{...again a large expression...} &= {...still a large expression...}  \\
&= {... a final large expression...}
\end{align} 

If \nonumber is not used, latex will assign numbers to every line break which for the majority of cases is useless. That worked for me