%% 
%%  Ein Beispiel der DANTE-Edition
%%  
%%  7. Auflage
%% 
%%  Beispiel 32-03-26 auf Seite 739.
%% 
%%  Copyright (C) 2016 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[]{exaarticle}
\pagestyle{empty}
\setlength\textwidth{145.16928pt}
\setlength\parindent{0pt}
%StartShownPreambleCommands
\usepackage{pst-optexp}
%StopShownPreambleCommands
\begin{document}
\begin{pspicture}[showgrid](0,-0.3)(3,3.3)
  \pnode(0,2.5){A}\pnode(2,2.5){B}\pnode(2,1.5){C}
  \mirror[labelangle=-45](A)(B)(C){M}
  \optbox[position=start, labeloffset=0,
    labelref=relative](C)(B){box}
  \drawbeam(A){1}{2}
  \psdot(A)\uput[90](A){A}\psdot(B)
  \uput[-135](B){B}\psdot(C)\uput[45](C){C}
\end{pspicture}
\end{document}
