10Sin²x + 2Sin2x -3*1 = 0
10Sin²x + 4SinxCosx - 3(Sin²x + Cos²x) = 0
10Sin²x + 4SinxCosx - 3Sin²x - 3Cos²x = 0
7Sin²x +4SinxCosx -3Cos²x = 0 | : Cos²x
7tg²x +4tgx -3 = 0
решаем как квадратное
D = 100
a) tgx = 6/14= 3/7
х = arctg(3/7) +πk , k ∈Z
б) tgx = -1
x = -π/4 + πn , n ∈Z