Помогите решить 11sin2x-7cos2x=11

22SinxCosx - 7 (Cos²x - Sin²x) = 11*1

22SinxCosx - 7Cos²x + 7Sin²x = 11 * (Sin ²x + Cos²x)

22SinxCosx - 7Cos²x + 7Sin²x = 11Sin ²x + 11Cos²x

22SinxCosx - 7Cos²x + 7Sin²x - 11Sin ²x - 11 Cos²x = 0

22SinxCosx - 18Cosx - 4Sin²x = 0

11SinxCosx - 9Cos²x - 2Sin²x = 0 | : Cos²x ≠ 0

11tgx - 9 - 2tg²x = 0

tgx = e

2y² - 11y + 9 = 0

D = b² - 4ac = 121 - 72 = 49

y₁ = (11+7) / 4 = 18/4=9/2=4,5

у₂ = (11-7) / 4 = 1

а) у₁ = 4,5

tgx = 4,5

x = arctg4,5 + πk, k ∈Z

б) у₂ = 1

tgx = 1

x = π/4 + πn, n ∈ Z