ta co$sin^2x-cos^2x+sinxcosx(sinx-cosx)=0=>sinx=cosx=sin(\frac\pi2-x)$
$=>x=\frac\pi2-x+k2\pi$ \/ $x=\frac\pi2+x+k2\pi$
hoac $sinx+cosx=-sinxcosx=-\frac{sin2x}2=>sin^2x+cos^2x+sin2x=\frac{sin^22x}4$
$=>sin^22x-4sin^22x-4=0=>sin2x=2^+_-\sqrt8=>sin2x=2-\sqrt8$
$=>2x=arcsin(2-\sqrt8)+k2\pi$ hoac $2x=\pi-arcsin(2-\sqrt8)+k2\pi$