11-7

> restart;

> x:=r*cos(t):y:=r*sin(t):
p:=plot3d([x,y,x^2-y^2],r=0..1,t=0..2*Pi,scaling=constrained,grid=[10,100],color=green):b;

> with(plottools):
vrml(p,"c:/program files/maple 6/beauty/11-7.wrl",background_color=white);

>

>