# Align all equal signs in the document

Is there a way to align all the equal signs in all equations all over the document? I write a theses (scrbook) and like all equal signs to line up. At least in a chapter if not possible for the whole document.

The \begin{align} or \begin{eqnarray} just do that for the small group. And to use \intertext for a whole chapter is unpractikal.

Example how it is at the moment:

\begin{align}
F_L^{\rightarrow}   & =     q ( E_{eFeld}^{\rightarrow} + v^{\rightarrow} \times B^{\rightarrow} )
\end{align}

much text

\begin{align}
F_{Lx}  & =     q ( E_{eFeld} + v_{gx} * B )
\end{align}

little text

\begin{align}
T   & =     F_{L1} - F_{L2}                                         \\
& =     q ( E_{eFeld} + v_{g1} * B - E_{eFeld} - v_{g2} * B )   \\
& =     q*B ( v_{g1} - v_{g2} )
\end{align}

\subsection{new subsection}

very little text

\begin{align}
P_{Photon}  & =     hf * nAc                \\
& =     \frac{E_{Photon}}{t}
\end{align}

more text

\begin{align}
F_{0}       & =     2nhfA               \\
& =     \frac{2 P_{Photon}}{c}
\end{align}


And I would like to have something like:

A  = b+C

Text

A  = longe equation

B  = also nice equation


And so on. I guess you get what I want. Can you help me? Thank you

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This does not sound like a good idea; one equation with a long left-hand side will force all the others to be indented. Perhaps you would prefer to be using the fleqn option, that sets all equations with a fixed indent from the left margin, rather than centered. – Andrew Swann Jul 2 '13 at 10:17
I tried fleqn. It looks not good. If there are sutch unplesant left-hand equations I guess there it a way to exclude them from the alignment like it is with the numbering. – Göran Jul 2 '13 at 10:30
But if you insist upon it, see tex.stackexchange.com/questions/115534/align-separate-equations/… where I created the algneqn environment – Steven B. Segletes Jul 2 '13 at 10:31
Thanks. Now I have the problem that the algneqn changes the sice of the \frac{}{}. It becomes pushed together to fit on a line. Can you help with that. (I tried to chance the definition of algneqn from equation to align and equnarry what both created errors) – Göran Jul 2 '13 at 11:11
unrelated to question but don't do P_{Photon} math italic is designed to make adjacent letters not look like a word. use P_{\mathrm{Photon}} or P_{\mathit{Photon}} – David Carlisle Jul 2 '13 at 11:41

Starting with my answer on align separate equations, I found I needed to change a few things, specifically because the OP for this question wanted to include multiline equations. As such, I had to reinstate \arraystretch to a non-zero value (in fact, I set it to 1.2). But with that, I had to do some \vspace manipulations going into and out of the algneqn environment I created.

But in the end, all the equal signs are aligned, per the OP's request. Setting the values of \leftalgn and \rightalgn will determine where on the overall line the alignment tab will be set.

\documentclass{article}
\usepackage{amsmath}
\def\leftalgn{0.3}\def\rightalgn{0.6}
\def\algnrow{\rule{\leftalgn\textwidth}{0ex}&\rule{\rightalgn\textwidth}{0ex}}
% CONSTRAINTS:
% equation label must fit in {1 -\leftalgn -\rightalgn}\textwidth
% \leftalgn must be larger than any text to left of align character
% \rightalgn must be larger than any text to right of align character
\newenvironment{algneqn}{%
\vspace{-1.6\baselineskip}%
\arraycolsep=0ex\renewcommand\arraystretch{1.2}%
$$% \begin{array}{rl}% \algnrow\\% }% {\\\algnrow% \end{array}\vspace{-\baselineskip}%$$\ignorespacesafterend%
}
\def\snug#1{\vspace*{-#1\baselineskip}}
\begin{document}
\begin{algneqn}
F_L^{\rightarrow}   & =     q ( E_{eFeld}^{\rightarrow} + v^{\rightarrow} \times B^{\rightarrow} )
\end{algneqn}

much text

\begin{algneqn}
F_{Lx}  & =     q ( E_{eFeld} + v_{gx} * B )
\end{algneqn}

little text

\begin{algneqn}
T   & =     F_{L1} - F_{L2}                                         \\
& =     q ( E_{eFeld} + v_{g1} * B - E_{eFeld} - v_{g2} * B )   \\
& =     q*B ( v_{g1} - v_{g2} )
\end{algneqn}

\subsection{new subsection}

very little text

\begin{algneqn}
P_{Photon}  & =     hf * nAc                \\
& =     \dfrac{E_{Photon}}{t}
\end{algneqn}

more text

\begin{algneqn}
F_{0}       & =     2nhfA               \\
& =     \dfrac{2 P_{Photon}}{c}
\end{algneqn}
\end{document}


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