%% 
%%  Die DANTE-Edition
%%  Ein Beispiel der LaTeX Referenz
%%  3. Auflage
%% 
%% 
%%  Copyright (C) 2013 Herbert Voss
%% 
%%  It may be distributed and/or modified under the conditions
%%  of the LaTeX Project Public License, either version 1.3
%%  of this license or (at your option) any later version.
%% 
%%  See http://www.latex-project.org/lppl.txt for details.
%% 
%% 
%% ==== 
% Show page(s) 1
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%% 
\documentclass[]{examargin}
\pagestyle{empty}
\setlength\textwidth{352.81416pt}
\setlength\parindent{0pt}
%StartShownPreambleCommands
\usepackage{amsmath,xcolor} \newcommand*\dx{\mathrm{d}x}
%StopShownPreambleCommands
\begin{document}
\begin{flalign}  f(x) & = \int\frac{1}{x^2}\,\dx \end{flalign}
\begin{flalign}
  f(x) & = \color{magenta}\int\frac{1}{x^2}\,\dx & % <-- dummy &
\end{flalign}
\end{document}