> restart;

> x:=cos(t):

> y:=sin(t):

> z1:=-1:

> z2:=cos(2*t):

> z:=(1-s)*z1+s*z2:

> a:=plot3d([x,y,z],s=0..1,t=0..2*Pi,scaling=constrained,grid=[5,50],color=green):

> a;

> x:=r*cos(t):

> y:=r*sin(t):

> z:=x^2-y^2:

> b:=plot3d([x,y,z],r=0..1,t=0..2*Pi,scaling=constrained,grid=[10,100],color=yellow):

> b;

> with(plots):

Warning, the name changecoords has been redefined

> c:=display(a,b):

> c;

> with(plottools):

Warning, the name changecoords has been redefined

> vrml(c,"c:/My Documents/mei/11.html/11-9.wrl",background_color=white):

>