%% 
%%  Ein Beispiel der DANTE-Edition
%%  
%%  7. Auflage
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%%  Beispiel 29-02-8 auf Seite 639.
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%%  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{169.16928pt}
\setlength\parindent{0pt}
%StartShownPreambleCommands
\usepackage{pstricks-add}
%StopShownPreambleCommands
\begin{document}
\psset{unit=0.5cm}
\begin{pspicture}(-5,-4)(5,5)
  \psaxes[dx=2,dy=2,Dx=2,Dy=2]{->}(0,0)(-5,-4)(5,5)
  \psline[linecolor=red](-5,-1)(5,5)
  \psline[linecolor=blue](-5,4)(5,-4)
  \qdisk(-5,-1){3pt}\uput[-90](-5,-1){A}
  \qdisk(5,5){3pt}  \uput[-90](5,5){B}
  \qdisk(-5,4){3pt} \uput[-90](-5,4){C}
  \qdisk(5,-4){3pt} \uput[-90](5,-4){D}
  \psIntersectionPoint(-5,-1)(5,5)(-5,4)(5,-4){P}
  \qdisk(P){2pt}   \uput{0.3}[90](P){P}
  \psline[linestyle=dashed](P|0,0)(P)(0,0|P)
\end{pspicture}
\end{document}