7cos2x+3sin²2x=3 помогите

7cos2x + 3sin^2 (2x) = 3

7cos2x + 3sin^2 (2x) - 3 = 0

7 cos (2x) - 3cos^ (2x) = 0

cos (2x) * (3cos (2x-7)) = 0

1) cos2x = 0

2x = π/2 + πn, n∈Z

x = π/4 + (πn) / 2, n∈Z

2) 3cos (2x) 7

cos (2x) = 7/3

2x = c0s^ (-1) (7/3) + πk, k∈Z

x2 = 1/2cos^ (-1) (7/3) + πk, k∈Z

2x = 2πm - cos^ (-1) (7/3) + πm, m∈Z

x3 = πm - (1/2) * cos^ (-1) (7/3), m∈Z