9709 P33 - Jun 2010 - Q7
1718
(i) Prove the identity \(\cos 3\theta \equiv 4 \cos^3 \theta - 3 \cos \theta\).
(ii) Using this result, find the exact value of \(\int_{\frac{1}{3}\pi}^{\frac{1}{2}\pi} \cos^3 \theta \, d\theta\).
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