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).
As for the syntax error, I suspect that is unrelated; there is an extra ";"
or "$" somewhere.
-s