How many distinct solutions of lie in the interval ?

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

Problem

How many distinct solutions of cos⁡x+cos⁡3x+cos⁡5x=0\cos x + \cos 3x + \cos 5x = 0 lie in the interval [0, 2π)[0,\,2\pi)? (a) 88 (b) 1010 (c) 99 (d) 1212

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