> restart:

> r:=sin(s):

> x:=r*cos(t):

> y:=r*sin(t):

> z:=cos(s):

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

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

> c:=plot3d ([x,y,z],s=0..Pi,t=Pi..3*Pi/2,color=blue,scaling=constrained):

> d:=plot3d ([x,y,z],s=0..Pi,t=3*Pi/2..2*Pi,color=yellow,scaling=constrained):

> with (plots):

Warning, the name changecoords has been redefined

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