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%%  Ein Beispiel der DANTE-Edition
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%%  1. Auflage
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%%  Beispiel 09-03-1 auf Seite 404.
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%%  Copyright (C) 2011 Herbert Voss
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%%  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.
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%%  See http://www.latex-project.org/lppl.txt for details.
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\documentclass[]{exaarticle}
\pagestyle{empty}
\setlength\textwidth{166.324pt}
\setlength\parindent{0pt}
\StartShownPreambleCommands

\StopShownPreambleCommands
\begin{document}
\[
  f(x)=\prod_{i=1}^{n}\left(i-\frac{1}{2i}\right)
\]
\begin{displaymath}
1+2+3+\cdots+n=\sum_{i=1}^n i=\frac{n(n+1)}{2}
\end{displaymath}
\end{document}