Mathematics 9709 · AS & A Level · Trigonometry

Trigonometry — practice question

(i)[3]

Express $8\cos\theta + 15\sin\theta$ in the form $R\cos(\theta - \alpha)$, where $R > 0$ and $0^\circ < \alpha < 90^\circ$. State $\alpha$ correct to 2 decimal places.

(ii)[4]

Hence, solve the equation $8\cos\theta + 15\sin\theta = 12$, giving every solution in the interval $0^\circ < \theta < 360^\circ$.

Worked solution & mark scheme

This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: State or indicate $R=17$

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