E-9. Show that 1/2 YO(0, ) = cos 8 Y(e, $) = - 3 1/2 e' sin e and Y,' (0, $) = 3 1/2 e- sin e 8 7 are orthonormal over the surface of a sphere. E-12. Show that the two functions fi(r) = e-cos0 and f2(r) = (2-re-/2 cos 0 are orthogonal over all space (in other words, over all possible values of r, 0, and )