(a Evaluate the gradient of the scalar field x2 2 f ( 2, y, z ) = 2 2 + 92 + 2 2 in spherical coordinates. Show that the same result is obtained by evaluating the gradient directly in Cartesian coordinates. (b) Show that Vx (rr) = 0 for any real number n where r = cityj + z k and r = 1/71