ĐKXĐ: \(sinx+cosx\ne0\)
=>\(\sqrt{2}\cdot sin\left(x+\dfrac{\Omega}{4}\right)\ne0\)
=>\(sin\left(x+\dfrac{\Omega}{4}\right)\ne0\)
=>\(x+\dfrac{\Omega}{4}\ne k\Omega\)
=>\(x=k\Omega-\dfrac{\Omega}{4}\)
Vậy: TXĐ là \(D=R\backslash\left\{-\dfrac{\Omega}{4}+k\Omega\right\}\)