## Precalculus (6th Edition) Blitzer

To plot the point $(r, \theta )=(3, 90^{\circ })$, begin with the $90^{\circ }$ angle. Because $90^{\circ }$ is a positive angle, draw $\theta = 90^{\circ }$ counterclockwise from the polar axis. Now consider $r=3$. Because $r \gt 0$, plot the point by going out three units on the terminal side of $\theta$ .