Use the fact that for all $\theta, \sin \left(\pi^8-\theta\right)=\sin \theta$ and $\cos \left(\pi^8-\theta\right)=-\cos \theta$ to prove that is a point $\mathbf{S}\left(x_1, y_1\right)$ has polar coordinates $(r, \theta)$ and a point $\mathbf{T}\left(x_2, y_2\right)$ has polar coordinates $\left(r, \pi^{\mathrm{R}}-\theta\right)$ then $x_1=-x_2$ and $y_1=y_2$.