`~rai~`
\(\tan\left[\dfrac{\pi}{4}(\sin x+1)\right]=1\\\Leftrightarrow \dfrac{\pi}{4}(\sin x+1)=\dfrac{\pi}{4}+k\pi\\\Leftrightarrow \sin x+1=1+4k\\\Leftrightarrow \sin x=4k.(k\in\mathbb{Z})\\\text{Do -1}\le\sin x\le 1\\\Rightarrow -1\le 4k\le 1\\\Leftrightarrow -\dfrac{1}{4}\le k\le\dfrac{1}{4}\\\text{mà k}\in\mathbb{Z}\Rightarrow k=0\\\text{Khi đó:}\sin x=0\\\Leftrightarrow x=n\pi.(n\in\mathbb{Z})\\\text{Vậy S=}\{n\pi|n\in\mathbb{Z}\}.\)
