Mathematics 9709 · AS & A Level · Trigonometry

Trigonometry — practice question

(a(i))[3]

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

(a(ii))[3]

Hence, solve $(\sqrt{5})\cos\left(\frac{x}{2}\right) + 2\sin\left(\frac{x}{2}\right) = 1.2$ for $0^\circ < x < 360^\circ$.

Worked solution & mark scheme

This 6-mark question has a full step-by-step worked solution and mark scheme. One marking point: The required value is $R=3$

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