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

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