How many distinct real solutions does the equation have in the open interval ?

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

Problem

How many distinct real solutions does the equation cos⁡4x=cos⁡2x\cos 4x = \cos 2x have in the open interval (0,2π)(0,2\pi)? (a) 4 (b) 7 (c) 5 (d) 6

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