%% 
%%  Ein Beispiel der DANTE-Edition
%% 
%% 
%%  Copyright (C) 2010 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{pstricks-add}
\newcommand\InitCond{ 0  0  5   10}
\newcommand\OMEGA{6.283185}
\newcommand\h{0.1}

\StopShownPreambleCommands
\begin{document}
\psset{unit=2}
\begin{pspicture}[showgrid=true](0,-2)(3,1.2)
  \psset{method=rk4,algebraic=true,whichabs=0,whichord=1}
  \psplotDiffEqn[linecolor=red,linewidth=1pt,plotpoints=500]
     {0}{10}{\InitCond}{y[2]|y[3]|\OMEGA*y[3]-\h*(sqrt(y[2]^2+y[3]^2))*y[2]|-\OMEGA*y[2]-\h*(sqrt(y[2]^2+y[3]^2))*y[3]}
  \psline{->}(0.5,1)
  \uput[90](0.5,1){$\overrightarrow{v}_0$}
  \pscircle{0.1}\psdot(0,0)
  \uput{3mm}[180](0,0){$\overrightarrow{B}$}
\end{pspicture}
\end{document}