Answer
The graph of $r=sin(\frac{9θ}{4}),~~0\leq θ\leq\frac{8\pi}{9}$
Work Step by Step
$y=cos~x$ is a periodic function. The domain required for an entire period is $2\pi$, that is, $0\leq x\leq2\pi$
$r=sin(\frac{9θ}{4})$
Domain required for an entire period:
$0\leq \frac{9θ}{4}\leq2\pi$
$0\leq θ\leq\frac{8\pi}{9}$
