Let f (r) be any spherically symmetric function; that is, when expressed in spherical polar coordinates, (r, θ, ∅), it has the form f (r) = f (r), independent of θ and ∅. (a) Starting from the definition (16.38) of ∇2 , prove that
(b) Prove the same result using the formula inside the back cover for ∇2 in spherical polar coordinates. (Obviously, this second proof is much simpler, but the hard work is hidden in the derivation of the formula for ∇2.)