On 5/7/07, Stavros Macrakis <macrakis at alum.mit.edu> wrote:
> On 5/6/07, Valery Pipin <pip at iszf.irk.ru> wrote:
> > ...
> F(th,ti):=realpart(expand(bx(.92,cos(th))*exp(%i*ti)));
> > ...
> > (%i214) contour_plot(F(x,y),[x,0,%pi],[y,0,3*%pi]);
> > 2
> > Is 1.0 - 1.0 cos (x) positive or negative?
> >
>
> Try quoting F(x,y), e.g. contour_plot( '( F(x,y) ), ...). It is probably
> trying to evaluate F at the symbolic value (x,y).
Also just writing the name of the function should work,
e.g. contour_plot(F, ...).
HTH
Robert