4 * + + 3 = 0 | * cos x4 * sin² x + 3 * cos x + 3 * cos² x = 0-cos² x + 3 * cos x + 4 = 0 | * (-1)cos² x - 3 cos x - 4 = 0cos x = t , t ∈ [-1 ; 1]t² - 3t - 4 = 0t₁ + t₂ = 3 t₁ = 4 , не подходит, т. к. t ∈ [-1 ; 1]t₁ * t₂ = -4 t₂ = -1cos x = -1x = π + 2πn, n ∈ z