y < 0\\ 0 & \mbox{if } x = 0 \mbox{ and } y = 0 \end{cases}$$ and $r=\sqrt{x^2+y^2}$. For more information you can watch Polar Coordinates . share | improve this answer edited May 25 at 1:24 answered May 25 at 1:13 Gastón Burrull 479 2 19 feedback Your Answer