3. Partial derivatives with two variables (11.3). Compute fx, fy, fxx, fyy, fry, and fyx for each of the following. (a) f(x, y) = x2+ y2 (b) f ( x, y ) = = Vx - y (c) f (x,y) = sin(xy) (d) f ( x, y ) = exzy (e) f(x, y) = In(e* +y) (f) f (x, y) = tan-1(x2 + y2)