To convert the polar coordinates $r\angle\theta$ to components notation $(x,y)$ use: $$x=r\cos\theta\qquad\qquad y=r\sin\theta.$$

To convert from the cartesian coordinates $(x,y)$ to polar coordinates $r\angle\theta$ use $$r=\sqrt{x^2+y^2}\qquad\qquad \theta=\tan^{-1}\left(\frac{y}{x}\right)$$