Construct the graph of z = x2 - y2 above the unit circle.

> restart;

> x:=r*cos(t):

> y:=r*sin(t):

> z1:=-1:

> z2:=cos(2*t):

> with(plottools):

> plot3d([x,y,x^2-y^2],r=0..1,t=0..2*Pi,scaling=constrained,grid=[10,100]);

>