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%%  Ein Beispiel der DANTE-Edition
%%  Mathematiksatz mit LaTeX
%%  3. Auflage
%%  Beispiel 10-03-2 auf Seite 216.
%%  Copyright (C) 2018 Herbert Voss
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%%  of the LaTeX Project Public License, either version 1.3
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\renewcommand\theequation{10.\arabic{equation}}
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\begin{document}
\begin{equation} \begin{array}{rcl}
\underline{RS} & = & \left(\begin{array}{*8c}
01 & a4 & 55 & 87 & 5a & 58 & db & 9e\\ a4 & 56 & 82 & f3 & 1e & c6 & 68 & e5\\
02 & a1 & fc & c1 & 47 & ae & 3d & 19\\ a4 & 55 & 87 & 5a & 58 & db & 9e & 03
\end{array}\right)\\~\\
\left(\begin{array}{c}  s_{i,0}\\  s_{i,1}\\  s_{i,2}\\  s_{i,3}
\end{array}\right) & = & \underline{RS} \cdot
\left(\begin{array}{c}  m_{8i+0}\\ m_{8i+1}\\ \cdots\\ m_{8i+6}\\ m_{8i+7}
\end{array}\right)\\~\\
  S_{i} & = & \sum_{j=0}^{3}s_{i,j}\cdot2^{8j}\qquad i=0,1,...,k-1\\
  S & = & \left(S_{k-1},S_{k-2},...,S_{1},S_{0}\right)
\end{array}
\end{equation}
\end{document}