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%%  Ein Beispiel der DANTE-Edition
%%  Mathematiksatz mit LaTeX
%%  3. Auflage
%%  Beispiel 04-10-2 auf Seite 62.
%%  Copyright (C) 2018 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
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\documentclass[10pt]{screxa}
\pagestyle{empty}
\setlength\textwidth{170.40707pt}
\AtBeginDocument{\setlength\parindent{0pt}}
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\begin{document}
\[ \Delta = \| a_{ik} \| = \left|
 \begin{array}{ccccc}
   a_{11} & a_{12} & a_{13} & \cdots & a_{1n}\\
   a_{21} & a_{22} & a_{23} & \cdots & a_{2n}\\
   \vdots & \vdots & \vdots & \ddots & \vdots\\
   a_{n1} & a_{n2} & a_{n3} & \cdots & a_{nn}
 \end{array} \right| \]
\end{document}