As per the given question,
If $x=a(2 \theta-\sin 2 \theta)$ and $y=a(1-\cos 2 \theta)$, find $\frac{d y}{d x}$ when $\theta=\frac{\pi}{3}$
If $x=a(2 \theta-\sin 2 \theta)$ and $y=a(1-\cos 2 \theta)$, find $\frac{d y}{d x}$ when $\theta=\frac{\pi}{3}$