Sin²x-sin x*cos x=cos 2x
sin²x-sin x*cos x=1-2sin²x
3sin²x-sin x*cos x=1
3sin²x-sin x*cos x=sin²x+соs²x
2sin²x-sin x*cos x-cos²x=0
2sin x(sin x-cos x) +cos x(sin x -cos x)=0
(2sin x+cos x)(sin x-cos x)=0
2sin x+cos x=0. Sin x-cos x=0
2sin x=-cos x. sin x=cos x
tg x=-1/2. tg x=1
X=-arctg 1/2+пиn. X=пи/4+пиn