The figure below represents the graphs of parametric curve $x(t) = \sin(t)$, $y(t) = \frac{1}{2}\sin(2t)$, $0 \le t \le 2\pi$ and polar curve $r^2 = \cos(2\theta)$, $0\le \theta \le 2\pi$. Which curve corresponds to which equation?
I simply have no idea how to approach this, as it seems that $t$ doesn't have a direct relationship to $\theta$.