Помогите решить срочно 2sin^2x+15cos x+6=0

2sin²x + 15cosx + 6 =0 2(1-cos²x) + 15cosx + 6 = 0 2 - 2cos²x + 15cosx + 6 = 0 2cos²x - 15cosx - 8 = 0 cosx = t 2t² - 15t - 8 = 0 t₁ = (15+17)/4 = 8 t₂ = (15-17)/4 = -1/2 cosx = 8 ⇒ нет корней cosx = -1/2 x = 2π/3 + 2πn x = -2π/3 + 2πn Ответ: -2π/3 + 2πn, 2π/3 + 2πn; n∈Z