Show that if the polar graph of $r=f(\theta)$ is rotated counterclockwise around the origin through an angle $\alpha$, then $r=f(\theta-\alpha)$ is an equation for the rotated curve. [Hint: If $\left(r_{0}, \theta_{0}\right)$ is any point on the original graph, then $\left(r_{0}, \theta_{0}+\alpha\right)$ is a point on the rotated graph.]