5sin^2x-11cisx^2+3=0

5sin²x-11cos²x+3 = 05sin²x-11(1-sin²x)+3 = 05sin²x-11+11sin²x+3 = 016sin²x-8 = 016sin²x = 8sin²x = 1/2sin x = 1/√2 и sin x = -1/√2sin x = 1/√2 → x = (-1)^n·π/4+πnsin x = -1/√2 → x = (-1)^n·5π/4+πn, n∈Z