xbasc();/// @@prerequisite 
theta=0:.01:2*%pi;rho=sin(2*theta).*cos(2*theta);
polarplot(theta,rho); /// \sleftarrow{\normalfont an \( \R\sp{2}\) curve in polar coordinates (Figure~\ref{f:gr5})}\index{polarplot@\texttt{polarplot}}
xs2ps(0,'fig5'); /// @@prerequisite affectations 
unix(SCI+'/bin/BEpsf fig5'); /// @@prerequisite affectations  /// \sleftarrow{\normalfont calling a Unix script}