7sin2x-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