# Multiple, multi-line equations in amsmath

I am experiencing the following problem. I have multiple equations that need to be aligned and numbered, but some of them are too long to fit into one line.

Here is my small example:

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\huge Here are my equations:
\begin{align}
A & = B should be numbered \\
A & = C another very long equation which must be split at a resaonable place, but still numbered
\end{align}
\end{document} • Isn't this something for the multiline or split environments? – user31729 Aug 11 '16 at 17:37
• probably... It would be nice to get a definite answer that others could use. I am not sure how to use the "&". To which one does it refer: inner or outer environment? Is this similar to nested tables? – Yossi Gil Aug 11 '16 at 17:46
• I am pretty sure there are answers on this already here ... but I am too lazy to look after them ;-) – user31729 Aug 11 '16 at 17:47
• Sam here. Except, that my google search did not yield anything. I can write an answer, or let someone else try.. – Yossi Gil Aug 11 '16 at 17:49

Here are 3 possibilities, hopefully illustrative. I suppose there are two groups of alignment, and the second group has long equations:

\documentclass[11pt]{article}
\usepackage{mathtools}

\begin{document}

Here are my equations:

\begin{align}
\shortintertext{with \texttt{aligned}: }
A & = B & \text{should be } & \text{ numbered }\\
A & = C & \text{another very long } & \!\begin{aligned}[t] & \text{ equation which must be split} \\
& \text{ at a reasonable place,}\\
& \text{ but still numbered} \end{aligned}
\end{align}

\begin{align}
\shortintertext{with \texttt{aligned} again: }
A & = B & \text{should be } & \text{ numbered }\\
A & = C & \text{another very long } & \!\begin{aligned}[t]  \text{ equation which must be split} &   \\
\text{ at a reasonable place,} & \\
\text{ but still numbered} &  \end{aligned}
\end{align}

\begin{align}
\shortintertext{A variant with \texttt{multlined}: }
A & = B & \text{should be }        & \text{ numbered }                                            \\
A & = C & \text{another very long } & \!\begin{multlined}[t]  \text{ equation which must be split} \\
\text{ at a reasonable place,}\\[-0.8ex]
\text{ but still numbered}
\end{multlined}
\end{align}

\end{document} As are suggested in @Christian Hupfer comments above

\documentclass{article}
\usepackage{mathtools}

\begin{document}
\huge Here with multlined:
\begin{align}
A & = B should be numbered \\
A & = \begin{multlined}[t][0.7\textwidth]
C + another + very +\\
long + equation + which + \\
must + bev split + at + \\
a + resaonable + place, +  \\
but + still + numbered
\end{multlined}
\end{align}
or with split
\begin{align}
A = \; & B should be numbered \\
\begin{split}
A =\; & C + another + very +\\
&    long + equation + which + \\
&    must + bev split + at + \\
&    a + resaonable + place, +  \\
&    but + still + numbered
\end{split}
\end{align}
\end{document} • Ah, I mispelled the name: multlined is the correct name ;-) (+1) – user31729 Aug 11 '16 at 18:06
• @ChristianHupfer, I always struggle with its correct spelling too :-) – Zarko Aug 11 '16 at 18:09