¦^§@·~12

> with(plots):with(plottools): 

Warning, the name changecoords has been redefined
> x:=r*cos(t)/sqrt(2);

x := 1/2*r*cos(t)*sqrt(2)

> y:=r*sin(t);

y := r*sin(t)

> z:=5*(x^2+y^2);

z := 5/2*r^2*cos(t)^2+5*r^2*sin(t)^2

> a:=plot3d([x,y,z],t=0..2*Pi,r=0..1,scaling=constrained,color=red,grid=[100,20]):

> z:=6-7*x^2-y^2;

z := 6-7/2*r^2*cos(t)^2-r^2*sin(t)^2

> b:=plot3d([x,y,z],t=0..2*Pi,r=0..1,scaling=constrained,color=green,grid=[50,20]):

> c:=display(a,b):

> c;

[Maple Plot]

> vrml(c,"c:/042/12/12-12.wrl",background_color=white);

>