i'm working on a short program to put random points on a sphere , but i have some difficulties :
 i consider a sphere  where  i choose  n  points  with  "randpoint" then i plot it but it doesn't work if someone can help me to correct my program

here is the program :

>with(geom3d):
> with(plots):
> s2:=sphere(s3,x^2+y^2+z^2=1):
> sphere1:=(x,y,z,R)->[x+R*cos(phi)*cos(theta),y+R*cos(phi)*sin(theta),z+R*sin(phi)]: