a) If the equation z = 6(r^2)cos2 given in a cylindrical coordinate system is expressed in a Cartesian coordinate system (x,y,z), z=f(x,y). And when expressed in spherical coordinate system (,,), =0 or cos=C(sin^2)cos2.

At this time, find f(x,y) and C.

b) Converting the hyperbolic vortex given by the formula r = 3 into a Cartesian coordinate system, find x, y (enter using the parameter (theta))