Mathematics 9709 · AS & A Level · Trigonometry

Trigonometry — practice question

(i)[3]

Rewrite $(\sqrt{6})\sin x + \cos x$ in the form $R\sin(x + \alpha)$, where $R > 0$ and $0^{\circ} < \alpha < 90^{\circ}$. Give the exact value of $R$ and state $\alpha$ correct to $3$ decimal places.

(ii)[4]

Hence solve the equation $(\sqrt{6})\sin 2\theta + \cos 2\theta = 2$, for $0^{\circ} < \theta < 180^{\circ}$.

Worked solution & mark scheme

This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: The exact value is $R=\sqrt{7}$.

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