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%%  Example 04-01-20 
%%  Copyright (C) 2016 Herbert Voss
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\documentclass[]{screxa}
\pagestyle{empty}
\setlength\textwidth{328.62788pt}
\setlength\parindent{0pt}
%StartShownPreambleCommands

%StopShownPreambleCommands
\begin{document}
\[
  \int_{-1}^{+1}\frac{f(x)}{\sqrt{1-x^{2}}}\,\mathrm{d}x\approx\frac{\pi}{n}
     \sum_{i=1}^{n}f\left(\cos\left(\frac{2i-1}{2n}\right)\right)
\]
\end{document}
