Construct the portion of the cylinder x2 + z2 = 0.81 lying outside x2+ y2 =1.

> restart:

> r:=0.9:

> x:=r*cos(t):

> z:=r*sin(t):

> y1:=sqrt(1-z^2):

> y:=(1-s)*y1+s*1.5:

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

> b:=plot3d([(1-2*s)*x,y1,z],t=0..2*Pi,s=0..1,scaling=constrained,grid=[100,10],color=yellow):

> c:=plot3d([x,-y,z],t=0..2*Pi,s=0..1,scaling=constrained,grid=[100,10],color=red):

> d:=plot3d([(1-2*s)*x,-y1,z],t=0..2*Pi,s=0..1,scaling=constrained,grid=[100,10],color=yellow):

> with (plots):

Warning, the name changecoords has been redefined

> display(a,b,c,d);

>