Calculus 3

(8) (8 points) Consider the function f : R' + R, f(x, y) = ry. Determine at which points (x, y) E R2 this function is differentiable. Hint: You may use the Differentiability Theorem where applicable. Consider separately the cases that (r, y) lies in a fixed quadrant outside the coordinate axes, resp. on a coordinate axis but is not the origin, resp. is the origin