Sin2x=cos2x-sin^2x+1

Sin2x = cos2x - sin^2x + 1

2sinxcosx = cos^2x - sin^2x + cos^2x

sin^2x + 2sinxcosx - 2cos^2x = 0

Разделим обе части ур-я на cos^2x не = 0.

tg^2x + 2tgx - 2 = 0

1) tgx = - 1 - V3 = = = > X1 = arctg (-1 - V3)

2) tgx = - 1 + V3 = = = > X2 = arctg (-1 + V3)