Đáp án:
$4)
B=\sin x(2\sin^2x-2\sin x-1)\\
C=(\sin x+\cos x)(1-\sin x\cos x-\cos x+\sin x)$
Giải thích các bước giải:
$4)
B=2\sin^3x+\cos2x-\sin x\\
=2\sin^3x+1-2\sin^2x-\sin x\\
=\sin x(2\sin^2x-2\sin x-1)\\
C=\sin^3x+\cos^3x-\cos2x\\
=(\sin x+\cos x)(\sin^2x-\sin x\cos x+\cos^2x)-(\cos^2x-\sin^2x)\\
=(\sin x+\cos x)(1-\sin x\cos x)-(\cos x-\sin x)(\cos x+\sin x)\\
=(\sin x+\cos x)(1-\sin x\cos x-\cos x+\sin x)$
