Answer
$x=r \ \cos(\theta)$, $y=r \ \sin(\theta) $ .
Work Step by Step
The conversion of polar co-ordinates $(r, \theta)$ to rectangular coordinates $(x,y)$ can be expressed as:
$x=r \ \cos(\theta)$, $y=r \ \sin(\theta) $
where, $r=\sqrt{x^2+y^2}$ and $\theta=\tan^{-1}(\dfrac{y}{x})$
