%% 
%%  Ein Beispiel der DANTE-Edition
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%%  7. Auflage
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%%  Beispiel 32-05-35 auf Seite 800.
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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{352.81416pt}
\setlength\parindent{0pt}
\usepackage[utf8]{inputenc}
%StartShownPreambleCommands
\usepackage{pst-thick,pst-grad}
%StopShownPreambleCommands
\begin{document}
\psset{unit=0.5cm}
\begin{pspicture}(-1,-2)(20,3)
\psthick[stylethick=serpent,E=1.5]{0}{20}{\fonctionSinus{10}{2}}
\multido{\i=0+1}{21}{%
  \pnode(!/t \i\space def
    /dt 10 360 div def   /E 1.5 def
    \fonctionSinus{10}{2}
    /ds dx dup mul dy dup mul add sqrt def
    /dx dx ds div def  /dy dy ds div def
    /nx E 2 div dy mul neg def % normale x
    /ny E 2 div dx mul def % normale y
    /x1 x0 nx add def  /y1 y0 ny add def x1 y1 ){A}
  \psdot(A) \pnode(! /x2 x0 nx sub def /y2 y0 ny sub def x2 y2){B}
  \psdot(B) \psline(A)(B)}
\parametricplot[linestyle=dashed]{0}{20}{ t O t mul sin 2 mul }
\end{pspicture}
\end{document}