> restart;

> x:=0.5+0.5*cos(t);

> y:=0.5*sin(t);

> z1:=sqrt(1-x^2-y^2):

> z2:=-z1:

> z:=(1-s)*z1+s*z2:

> a:=plot3d([x,y,z],s=0..1,t=0..2*Pi,scaling=constrained,color=red,grid=[5,100]):

> x:=0.5+r*cos(t);

> y:=r*sin(t);

> z:=sqrt(1-x^2-y^2):

> b:=plot3d([x,y,z],r=0..0.5,t=0..2*Pi,scaling=constrained,color=pink,grid=[10,50]):

>

> c:=plot3d([x,y,-z],r=0..0.5,t=0..2*Pi,scaling=constrained,color=pink,grid=[10,50]):

> with(plots):

Warning, the name changecoords has been redefined

> d;

¦