% starfish.tex
%
% Elliptic curve in Edwards form given by E: x^2 + y^2 = 1 - 30x^2y^2 over the real numbers
%
% Author: Peter Schwabe
% Public domain

\psset{unit=2cm} 
  \begin{pspicture}(-1.5,-1.5)(1.5,1.5) 
  \psaxes{->}(0,0)(-1.5,-1.5)(1.5,1.5)  
  
  \psplot[plotstyle=curve]{-1}{1}{1 x x mul sub 1 30 x mul x mul add div sqrt}
  \psplot[plotstyle=curve]{-1}{1}{1 x x mul sub 1 30 x mul x mul add div sqrt neg}

\end{pspicture}