9. (a) Show that when Laplace's equation 2 2 33:; 6' u a u , + + = 0 6r 6y 2 is written in cylindrical coordinates, it becomes 1 + + 3 3 '1 at" 1' 6r 1" 36' 62' (b) Show that when Laplace's equation is written in spherical coordinates, it becomes 3 1 2 6'1: 2 6H (:01an 6n 1 Bu 1 6H , ++ ap' 1 + 1 1 + f 1 =0 9 69 p" 6d) p" 6d" p\"SIn'v 69\