\documentclass[pstricks]{standalone}
\usepackage{pst-contourplot,pst-math}
\begin{document}
\begin{pspicture}(-5,-5)(5,5)
% https://www.maplesoft.com/applications/view.aspx?sid=1582&view=html
\psframe*[linecolor=cyan](-5,-5)(5,5)
\psset{unit=0.5}%
\psContourPlot[a=0.1,linecolor=red,Fill,fillcolor=yellow,ReverseColors,function=x y SIN 2 mul add SIN y x COS 3 mul add COS sub](-10,-10)(10,10)
\end{pspicture}
\end{document} 