> restart:

> with (plottools):

> r:=sqrt(2)/2:

> a1:=sphere([1,0,0],r):

> a2:=sphere([-1,0,0],r):

> a3:=sphere([0,1,0],r):

> a4:=sphere([0,-1,0],r):

> a5:=sphere([0,0,1],r):

> a6:=sphere([0,0,-1],r):

> with (plots):

> display (a1,a2,a3,a4,a5,a6,scaling=constrained);