Answer
-$\frac{\pi}{2}\leq \Theta \leq \frac{\pi}{2} $ ,$1\leq r \leq 4$
Work Step by Step
Describing the given region in polar cordinates of the given graph
$x^2+y^2=1^2$
=> $r=1$
$x^2+y^2=4^2$
$r=4$
=-$\frac{\pi}{2}\leq \Theta \leq \frac{\pi}{2} $ ,$1\leq r \leq 4$
