Which of the following gives the correct value of ?

MATHEMATICS · Single correct · A Level · Mathematics · Trigonometry · Trigonometry

Problem

Which of the following gives the correct value of cos⁡3θ\cos 3\theta? (a) 3cos⁡θ−4cos⁡3θ3\cos\theta-4\cos^{3}\theta (b) 3cos⁡3θ−4cos⁡θ3\cos^{3}\theta-4\cos\theta (c) 4cos⁡3θ−3cos⁡θ4\cos^{3}\theta-3\cos\theta (d) 4cos⁡3θ+3cos⁡θ4\cos^{3}\theta+3\cos\theta

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