ĐKXĐ:
a. \(x-1\ne0\Rightarrow x\ne1\)
b. \(sinx+1>0\Rightarrow sinx\ne-1\Rightarrow x\ne-\dfrac{\pi}{2}+k2\pi\)
c. \(cos\left(2x-\dfrac{\pi}{6}\right)\ne0\Rightarrow2x-\dfrac{\pi}{6}\ne\dfrac{\pi}{2}+k\pi\Rightarrow x\ne\dfrac{\pi}{3}+\dfrac{k\pi}{2}\)
d. \(cos\left(3x-\pi\right)\ne0\Rightarrow cos3x\ne0\Rightarrow3x\ne\dfrac{\pi}{2}+k\pi\Rightarrow x\ne\dfrac{\pi}{6}+\dfrac{k\pi}{3}\)
e. \(sin^2x-cos^2x\ne0\Rightarrow cos2x\ne0\Rightarrow2x\ne\dfrac{\pi}{2}+k\pi\Rightarrow x\ne\dfrac{\pi}{4}+\dfrac{k\pi}{2}\)
g. \(cos2x-1\ne0\Rightarrow cos2x\ne1\Rightarrow2x\ne k2\pi\Rightarrow x\ne k\pi\)