Answer
The graph of $r=cos(\frac{θ}{3}),~~0\leq θ\leq6\pi$
Work Step by Step
$y=cos~x$ is a periodic function. The domain required for an entire period is $2\pi$, that is, $0\leq x\leq2\pi$
$r=cos(\frac{θ}{3})$
Domain required for an entire period:
$0\leq \frac{θ}{3}\leq2\pi$
$0\leq θ\leq6\pi$
