%% 
%%  Ein Beispiel der DANTE-Edition
%% 
%% 
%%  Copyright (C) 2008 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{214.324pt}
\setlength\parindent{0pt}
\StartShownPreambleCommands
\usepackage{pst-func}
\StopShownPreambleCommands
\begin{document}
\begin{pspicture*}(-3,-2.2)(3.5,2.5)
\psaxes{->}(0,0)(-3,-2)(3.2,2)
\psplotImp[linewidth=2pt](-5,-2.2)(5,2.4){
  /xqu x dup mul def /yqu y dup mul def
  xqu yqu add dup mul 2 dup
  add 2 mul xqu yqu sub mul sub }
\rput*(2,1.5){%
  $\left(x^2+y^2\right)^2-8(x^2-y^2)=0$}
\psplotImp[linewidth=1pt,linecolor=red,
  algebraic](-5,-2.2)(5,2.4){%
   (x^2+y^2)^2-4*(x^2-y^2) }% Lemniskate a=2
\end{pspicture*}
\end{document}
