\(y=\dfrac{2\sin x}{\cos\left(x+1\right)}\\ ĐK:\cos\left(x+1\right)\ne0\\ \Leftrightarrow x\ne k2\pi-1\)
y=2sinxcos(x+1)
dk :cos(x+1)≠0
= x≠k2π−1
\(y=\dfrac{2sinx}{cos\left(x+1\right)}\)
Hàm số xác định khi: \(cos\left(x+1\right)\ne0\Leftrightarrow x+1\ne\dfrac{\pi}{2}+k\pi\Leftrightarrow x\ne\dfrac{\pi}{2}-1+k\pi\)