(i)[3]
Show that $\sin^4 \theta - \cos^4 \theta \equiv 2\sin^2 \theta - 1$ by simplifying the left-hand side.
(ii)[4]
Hence solve the equation $\sin^4 \theta - \cos^4 \theta = \frac{1}{2}$ over the interval $0^\circ \leq \theta \leq 360^\circ$.
Mathematics 9709 · AS & A Level · Trigonometry
Trigonometry — practice question
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This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Use the algebra correctly to reach $(s^2 - c^2)(s^2 + c^2)$, or an equivalent expression.” …
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