xbasc();/// @@prerequisite 
function [x,y,z]=f3(alpha,theta) 
  x=cos(alpha).*cos(theta);
  y=cos(alpha).*sin(theta);
  z=sinh(alpha);
endfunction
alphagrid=linspace(-%pi/2,%pi/2,40);thetagrid=linspace(0,2*%pi,20);
[x1,y1,z1]=eval3dp(f3, alphagrid, thetagrid); /// \sleftarrow{\normalfont building a set of facets } \index{eval3dp@\texttt{eval3dp}}
plot3d1(x1,y1,z1); /// \sleftarrow{\normalfont an  \( \R\sp{3}\) surface composed by a set of facets (Figure~\ref{f:gr6})}
xs2ps(0,'fig6');/// @@prerequisite affectations 
unix(SCI+'/bin/BEpsf fig6'); /// @@prerequisite affectations  /// \sleftarrow{\normalfont calling a Unix script}