Помогите решить тригонометрические уравнения 1)18tg^2x+3tgx-10=0
2)5cosx-2sinx=0
3)4cos^2x+3cosx=0

1) 18tg²x + 3tgx - 10 = 0Пусть t = tgx.18t² + 3t - 10 = 0D = 9 + 4•10•18 = 729 = 27²t1 = (-3 + 27)/36 = 24/36 = 2/3t2 = (-3 - 27)/36 = -30/36 = -5/6Обратная замена:tgx = 2/3x = arctg(2/3) + πn, n ∈ Ztgx = -5/6x = arctg(-5/6) + πn, n ∈ Z.2) 5cosx - 2sinx = 0 -2tgx + 5 = 0-2tgx = -5tgx = 2/5x = arctg(2/5) + πn, n ∈ Z.3) 4cos²x + 3cosx = 0cosx(4cosx + 3) = 0cosx = 0x = π/2 + πn, n ∈ Z4cosx + 3 = 04cosx = -3cosx = -3/4x = ±arccos(-3/4) + 2πn.