Respuesta :

Answer:

x = 0, 2π/3, 4π/3, 2π.

Step-by-step explanation:

cos 2x = 2cos^2x - 1 so

2cos^2x - 1 = cos x

2cos^2x - cos x - 1 = 0

(2cosx + 1)(cos x - 1) =0

cos x = -1/2, 1.

When cos x = 1, x = 0, 2π

when cos x = -1/2, x = 2π/3, 4π/3.

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