Mathematics 9709 · AS & A Level · Trigonometry

Trigonometry — practice question

(i)[5]

Start by expanding $2\sin(x - 30^\circ)$, then rewrite $2\sin(x - 30^\circ) - \cos x$ in the form $R\sin(x - \alpha)$, where $R > 0$ and $0^\circ < \alpha < 90^\circ$. State the exact value of $R$ and the value of $\alpha$ correct to 2 decimal places.

(ii)[3]

Hence solve $2\sin(x - 30^\circ) - \cos x = 1$, for $0^\circ < x < 180^\circ$.

Worked solution & mark scheme

This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: Apply the $\sin(A-B)$ formula and rewrite the result using only $\sin x$ and $\cos x$

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