12-6.Construct the part of the sphere
x2 + y2 + z2 =1
lying outside the cylinder
(x - 0.5)2 + y2 = 0.25.

> restart:

> with(plots):with(plottools):

Warning, the name changecoords has been redefined

> r:=cos(t):

> x:=r*cos(s):

> y:=r*sin(s):

> z:=(1-r^2)^(1/2):

> a:=plot3d([x,y,z],s=t..2*Pi-t,t=0..Pi/2,scaling=constrained,color=pink):

> b:=plot3d([x,y,-z],s=t..2*Pi-t,t=0..Pi/2,scaling=constrained,color=gray):

> p:=display(a,b):

> p;

> vrml(p,"c:/program files/maple 6/beauty/12-6.wrl",background_color=white);

>