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sin²x+sinxcosx-2sinxcosx-2cos²x=0
sinx(sinx+cosx)-2cosx(sinx+cosx)=0
(sinx+cosx)(sinx-2cosx)=0
sinx+cosx=0 v sinx-2cosx=0
sinx=-cosx /:cosx v sinx=2cosx
tgx=-1 v tgx=2
..........
2.
cos2x=cosx
2x=x+2kπ v 2x=-x+2kπ , k∈ Z
x=2kπ v 3x=2kπ
x=2kπ v x=2/3 kπ