Rút gọn: A= $\frac{sin(\pi+x)cos(x- \frac{\pi}{2} )tan(7\pi+x)}{cos(5\pi-x)sin(\frac{3\pi}{2}+x)tan(2\pi+x)}$ 30/08/2021 Bởi Brielle Rút gọn: A= $\frac{sin(\pi+x)cos(x- \frac{\pi}{2} )tan(7\pi+x)}{cos(5\pi-x)sin(\frac{3\pi}{2}+x)tan(2\pi+x)}$
$A=\dfrac{\sin(x+\pi).\cos\Big(\dfrac{\pi}{2}-x\Big).\tan(x+7\pi)}{ \cos(4\pi+\pi-x).\sin(2\pi-\dfrac{\pi}{2}+x\Big).\tan(\pi+\pi+x\Big)}$ $=\dfrac{-\sin x.\sin x.\tan x}{\cos(\pi-x).\sin\Big(\dfrac{\pi}{2}-x\Big).\tan x}$ $=\dfrac{-\sin^2x}{-\cos x.\cos x}$ $=\tan^2x$ Bình luận
$A=\dfrac{\sin(x+\pi).\cos\Big(\dfrac{\pi}{2}-x\Big).\tan(x+7\pi)}{ \cos(4\pi+\pi-x).\sin(2\pi-\dfrac{\pi}{2}+x\Big).\tan(\pi+\pi+x\Big)}$
$=\dfrac{-\sin x.\sin x.\tan x}{\cos(\pi-x).\sin\Big(\dfrac{\pi}{2}-x\Big).\tan x}$
$=\dfrac{-\sin^2x}{-\cos x.\cos x}$
$=\tan^2x$