Решите уравнение: cos x * (2cos x - cos 3x) = 1.
cos x * (2cos x - cos 3x) = 1 2cos^2 x - cos x cos 3x = 1 cos 2x - (cos 2x + cos 4x)/(2) = 0 cos 2x - cos 4x = 0 2cos^2 2x - cos 2x - 1 = 0 (2cos 2x + 1)(cos 2x - 1) = 0 [arrayl cos 2x = -(1)/(2) cos 2x = 1 array. 2x = (2pi k)/(3), k in Z x = (pi k)/(3), k in Z.
\( x = \frac{\pi k}{3},\ k \in \mathbb{Z} \)