Answer
$r = \theta$
Work Step by Step
The red graph shows $r = \theta$ for values of $\theta$ such that $0 \leq \theta \leq \frac{20\pi}{3}$
The violet graph shows $r = \theta$ for values of $\theta$ such that $-\frac{20\pi}{3} \leq \theta \leq 0$
Note that $r = 0$ when $\theta = 0$, and the magnitude of $r$ continues to increase as the magnitude of $\theta$ increases. This leads to a spiral shape. There is symmetry in the graph about the vertical axis since we include both positive and negative values of $\theta$
