\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage[latin1]{inputenc}
\usepackage{pstricks,pstricks-add}
\usepackage{lmodern}
\parindent=0pt
\pagestyle{empty}

\begin{document}

\psset{unit=5}
\psset{method=rk4, algebraic=true, whichabs=0, whichord=1,
    plotpoints=500,linewidth=1pt}

\begin{pspicture}(-1.2,-0.2)(1.2,0.2)
  \psgrid[subgriddiv=5,subgridcolor=black!10,gridlabels=7pt](-1.2,-0.2)(1.2,0.2)
  \psplotDiffEqn[linecolor=red]{0}{12}{0 0 0 0}{%
    y[2]|y[3]|6.283185*y[3]|4*cos(0.6283185*x)-6.283185*y[2]}
\end{pspicture}


%\begin{verbatim}
%  \psplotDiffEqn[linecolor=red]{0}{12}{0 0 0 0}{%
%    y[2]|y[3]|6.283185*y[3]|4*cos(0.6283185*x)-6.283185*y[2]}
%\end{verbatim}

\bigskip
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  \psgrid[subgriddiv=5,subgridcolor=black!10,gridlabels=7pt](-1.2,-0.2)(1.2,0.2)
  \parametricplot[plotpoints=500,linecolor=blue]{0}{12}{%
    4/(6.283185^2-(0.6283185)^2)*(sin(0.6283185*t)/0.1-sin(6.283185*t))|% 
    4/(6.283185^2-(0.6283185)^2)*(cos(0.6283185*t)-cos(6.283185*t))}
\end{pspicture}

%\begin{verbatim}
%  \parametricplot[plotpoints=500,linecolor=blue]{0}{12}{%
%    4/(6.283185^2-(0.6283185)^2)*(sin(0.6283185*t)/0.1-sin(6.283185*t))|% 
%    4/(6.283185^2-(0.6283185)^2)*(cos(0.6283185*t)-cos(6.283185*t))}
%\end{verbatim}

\end{document}



