Respuesta :

DeanR

Let's check.

x = 5π/24

4x = 5π/6

cos 4x = cos(5π/6) = cos 150° = -√3/2

cos² 4x = (-√3/2)^2 = 3/4

4 cos² 4x  -3  = 4 (3/4) - 3 = 0

Answer: TRUE