Answer
$(0,3)$
Work Step by Step
By definition: $x=r\cdot \cos(\theta)$, $y=r\cdot \sin(\theta)$.
Here, we have $r=3 \text{ and } \theta=\frac{\pi}{2}$.
Hence, after plugging these in:
$x=3\cdot \cos(\frac{\pi}{2})=3\cdot0=0$,
$y=3\cdot \sin(\frac{\pi}{2})=3\cdot1=3.$
The point has coordinates $(0,3)$ in the rectangular coordinate system.