Question

sin²x-sin2x-3cos²x=0

Answer 1

sin^2 x-2sin x cos c - 3 cos^2 x = 0
( : cos ^ 2 x) 
tg ^ 2 x - 2 tg x - 3 = 0
tg x = t
t^2 - 2t - 3 =0
t1 = 3
t2 = -1
1) tg x = 3
x = arctg 3  + pi n 
2) tg x = -1
x =  - pi / 4 + pi n