Mathematics 9709 · AS & A Level · Trigonometry

Trigonometry — practice question

(i)[3]

Express $3\cos\theta + \sin\theta$ in the form $R\cos(\theta - \alpha)$, where $R > 0$ and $0^\circ < \alpha < 90^\circ$, and state the exact value of $R$ together with the value of $\alpha$ correct to $2$ decimal places.

(ii)[5]

Hence solve the equation $3\cos 2x + \sin 2x = 2$, and list all solutions in the interval $0^\circ \leq x \leq 360^\circ$.

Worked solution & mark scheme

This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: State that $R = \sqrt{10}$

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