For the parametric equation $ x = 3 \left( \theta - \sin \theta \right) , y = 3 \left( 1 - \cos \theta \right) $ find the derivative

Question

Apologies if this question is a bit too easy for everyone.

For the curve defined by the parametric equations $ x = 3 \left( \theta - \sin \theta \right) , y = 3 \left( 1 - \cos \theta \right) $ for $ 0 \leq \theta \leq \pi $, what is the derivative $ \frac{dy}{dx} $ in terms of $\theta$?

Seen questions a bit like this before, used the chain rule but not sure how to approach this question. Thanks.

Answer 1

$$\frac{dy}{dx}=\frac{dy/d\theta}{dx/d\theta}=\frac{3 \sin \theta}{3-3\cos \theta}=\frac{\sin \theta}{1-\cos \theta}$$