Помогите решить!!! sin2x-22cos^2x+10=0

7sin2x-22cos^2x+10=0 14sinxcosx - 22cos^2x + 10(sin^2x + cos^2x) = 0 14sinxcosx -12cos^2x +10sin^2x = 0  |:cos^2x 14tgx - 12 + 10tg^2x = 0 5tg^2x +7tgx - 6 = 0 tgx = t 5t^2 +7t - 6 = 0 D = 49 + 4*5*6 = 169 t = (-7 +- 13)/10 t = -2   t = 3/5 tgx = -2                            tgx = 3/5 x = -arctg2 + Пk                x = arctg(3/5) + Пk