%% 
%%  A DANTE-Edition example
%% 
%% 
%%  Copyright (C) 2011 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[]{article}
\pagestyle{empty}
\setlength\textwidth{201.70511pt}
\setlength\parindent{0pt}

\usepackage{pstricks-add,pst-func,multido}

\begin{document}
\begin{pspicture*}(-5,-2)(5.5,2)
  \pscircle(0,0){1}\psaxes{->}(0,0)(-5,-1.5)(5.5,2)
  \multido{\rA=0.01+0.2}{5}{%
    \psplotImp[linewidth=1pt,linecolor=blue,polarplot](-6,-6)(5,2.4){
	 r dup mul 1.0 r div sub phi sin dup mul mul \rA\space sub }}
  \rput[lb](0.5,1.3){$f(r,\phi)=\left(r^2-\frac{1}{r}\right)\times\sin^2\phi=0$}
\end{pspicture*}
\end{document}
