Гите с уровнением 6sin^2x + 5cosx -5 = 0

6·sin²x + 5·cos x - 5 = 0
6·(1 - cos²x) + 5·cos x - 5 = 0
6 - 6·cos²x + 5·cos x - 5 = 0
- 6·cos²x + 5·cos x + 1 = 0
6·cos²x - 5·cos x - 1 = 0
cos x = t
6t² - 5t -1 = 0
D = 25 + 24 = 49
t = (5 (+/-) 7)/12

t₁ = -1/6
t₂ = 1

cos x = -1/6
cos x = 1

x = (+/-) arc cos (-1/6) + 2πn, n ∈ Z
x = 2πk, k ∈ Z