> restart;

> x:=r*cos(t)/sqrt(2):y:=r*sin(t):

> z:=5*x^2+5*y^2:

> with(plots):

Warning, the name changecoords has been redefined

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

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

> c:=display(a,b):

> c;

> with(plottools):

> vrml(c,"c:/040/12/12-12.wrl",background_color=white):

>