9sinxcosx-7 cos2x=2sin^2x

Question

9sinxcosx-7 cos2x=2sin^2x

Answer 1

Вроде так..

2sin²x-9sinxcosx+7cos²x=0 (:cos²x≠0)

2tg²x-9tgx+7=0

tgx=y;2y²-9y+7=0;y₁=1;y₂=7/2

1) tgx=1;x=π/4+πn,n∈Z

2) tgx=7/2;x=arctg(7/2)+πk,k∈Z.