%% 
%%  Ein Beispiel der DANTE-Edition
%%  
%%  7. Auflage
%% 
%%  Beispiel 35-00-99 auf Seite 859.
%% 
%%  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
%% 
%% 
\documentclass[]{exaarticle}
\pagestyle{empty}
\setlength\textwidth{352.81416pt}
\setlength\parindent{0pt}
%StartShownPreambleCommands
\usepackage{pst-eucl,pst-plot}
%StopShownPreambleCommands
\begin{document}
\def\Angle{37}
\def\R{5}
\begin{pspicture}(-\R,-\R)(\R,\R)
    \pstGeonode[PointSymbol=none,PosAngle={45,-90},PointNameSep=24pt](\R;\Angle){B}(0,0){O}(\R;0){A}
    \pcline[linecolor=lightgray,linewidth=12pt,offset=-6pt,strokeopacity=0.6](O)(A)
    \pcline[linecolor=lightgray,linewidth=12pt,offset=6pt,strokeopacity=0.6](O)(B)
    \psline(B)(O)(A)
    \pstMarkAngle[MarkAngleRadius=1.6,LabelSep=.8]{A}{O}{B}{$\theta$}
    \pstGeonode(!3 \Angle\space 2 div PtoC){X}
    \color{blue}\psset{linecolor=blue}%
    \pstOrtSym{O}{A}{X}[I_1] \psline[linestyle=dotted](X)(I_1)
    \newif\ifA \Afalse
    \pstFPDiv\No{360}{\Angle}
    \multido{\iA=1+1,\iB=2+1}{\numexpr\No-1}{%
      \ifA\pstOrtSym{O}{A}{I_\iA}[I_\iB]\else\pstOrtSym{O}{B}{I_\iA}[I_\iB]\fi
      \psline[linestyle=dotted](I_\iA)(I_\iB)
      \ifA\Afalse\else\Atrue\fi
    }%
    \color{red}\psset{linecolor=red}%
    \pstOrtSym{O}{B}{X}[I_1] \psline[linestyle=dotted](X)(I_1)
    \newif\ifA \Atrue
    \pstFPDiv\No{360}{\Angle}
    \multido{\iA=1+1,\iB=2+1}{\numexpr\No-1}{%
      \ifA\pstOrtSym{O}{A}{I_\iA}[I_\iB]\else\pstOrtSym{O}{B}{I_\iA}[I_\iB]\fi
      \psline[linestyle=dotted](I_\iA)(I_\iB)
      \ifA\Afalse\else\Atrue\fi
    }%
    \pscircle[linestyle=dotted](O){3}
\end{pspicture}
\end{document}