PT \Leftrightarrow 4\sin x\cos x+2\sin ^{2}x-1-7\sin x-2\cos x+4=0\Leftrightarrow 2\cos x(2\sin x-1)+(2\sin x-1)(\sin x-3)=0\Leftrightarrow (2\sin x-1)(2\cos x+\sin x-3)=0$\sin x=0,5\Rightarrow x=\frac{\pi }{6}+2k\pi , or x=\frac{5\pi }{6}=2k\pi .hoặc :2\cos x+\sin x=3\Leftrightarrow (vô nghiệm vì 3>\sqrt{4+1})$kl
PT
\Leftrightarrow 4\sin x\cos x+2\sin ^{2}x-1-7\sin x-2\cos x+4=0\Leftrightarrow 2\cos x(2\sin x-1)+(2\sin x-1)(\sin x-3)=0\Leftrightarrow (2\sin x-1)(2\cos x+\sin x-3)=0$\sin x=0,5\Rightarrow x=\frac{\pi }{6}+2k\pi , or x=\frac{5\pi }{6}
+2k\pi .
hoặc :2\cos x+\sin x=3\Leftrightarrow
(vô nghiệm vì 3>\sqrt{4+1})$kl