Mathematics 9709 · AS & A Level · Differentiation

Differentiation — practice question

The curve is given in parametric form by $x = 2\sin\theta + \sin 2\theta$, $y = 2\cos\theta + \cos 2\theta$, where $0 < \theta < \pi$.
(i)[3]

Obtain an expression for $\frac{dy}{dx}$ in terms of $\theta$.

(ii)[4]

Hence find the exact coordinates of the point on the curve where the tangent is parallel to the $y$-axis.

Worked solution & mark scheme

This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: Obtain the derivatives $\frac{dx}{d\theta}=2\cos\theta+2\cos2\theta$ and $\frac{dy}{d\theta}=-2\sin\theta-2\sin2\theta$

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