Đáp án: $A=\cos(x)$
Giải thích các bước giải:
Ta có:
$A=\cos(3\pi-x)-2\sin(\dfrac{3\pi}2+x)+\tan(\dfrac{3\pi}{2}-x)+\cot(2\pi-x)$
$\to A=\cos(2\pi+\pi-x)-2\sin(2\pi-\dfrac{\pi}2+x)+\cot(\dfrac{\pi}{2}-(\dfrac{3\pi}{2}-x))+\cot(-x)$
$\to A=\cos(\pi-x)-2\sin(-\dfrac{\pi}2+x)+\cot(x-\pi)-\cot(x)$
$\to A=\cos(\pi-x)+2\sin(\dfrac{\pi}2-x)+\cot(x)-\cot(x)$
$\to A=-\cos(x)+2\cos(x)$
$\to A=\cos(x)$
