2sinxcosx-9sincosx+3cos2x+1=0
-7sinxcosx+3cos^2x-3sin^2x+cos^2x+sin^2x=0
4cos^2x-2sin^2x-7sinxcosx=0 :cos^2x
4-2tg^2x-7tgx=0
2s^2+7s-4=0
[-7+-sqrt(49+32)]/4
s1=-4
s2=1/2
x=arctg1/2+Пk
x=arctg(-4)+Пl
2sinxcosx-9sincosx+3cos2x+1=0
-7sinxcosx+3cos^2x-3sin^2x+cos^2x+sin^2x=0
4cos^2x-2sin^2x-7sinxcosx=0 :cos^2x
4-2tg^2x-7tgx=0
2s^2+7s-4=0
[-7+-sqrt(49+32)]/4
s1=-4
s2=1/2
x=arctg1/2+Пk
x=arctg(-4)+Пl