Please solve this question...

Problem 1.14 Suppose that f is a function of two variables (y and z) only. Show that the gradient Vf = (af/0y)ý +(0f/8z)2 transforms as a vector un- der rotations, Eq. 1.29. [Hint: (af/8y) = (8f/8y)(8y/8y) + (0f/az)(8z/0y), and the analogous formula for df/8z. We know that y= y cos o+ z sin ộ and Z=-y sino+zcos p; "solve" these equations for y and z (as functions of y and Z), and compute the needed derivatives 3y/8y, 3z/0y, ctc.]