Mathematics 9709 · AS & A Level · Trigonometry

Trigonometry — practice question

(i)[3]

Express $2 \cos \theta + \sqrt{5} \sin \theta$ in the form $R \cos(\theta - \alpha)$ where $R > 0$ and $0^\circ < \alpha < 90^\circ$, and give the value of $\alpha$ correct to 2 decimal places.

(ii)[4]

Hence determine the solutions of the equation $2 \cos \theta + \sqrt{5} \sin \theta = 1$ for $0^\circ < \theta < 360^\circ$.

Worked solution & mark scheme

This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: State that $R=3$

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