3cos3x+2cosx=0 help!!!!
По формуле cos3x = 4cos³x - 3cosx получаем: 3(4cos³x - 3cosx) + 2cosx = 0 12cos²x - 9cosx + 2cosx = 0 12cos²x - 7cosx = 0 cosx(12cosx - 7) = 0 cosx = 0 x = π/2 + πn, n ∈ Z 12cosx - 7 = 0 12cosx = 7 cosx = 7/12 x = ±arccos(7/12) + 2πn, n ∈ Z