Question

Find the domain of $f\left(x\right)={\cos }^{-1}x+\cos x$.

Answer 1

For ${\cos }^{-1}x$ to be defined.
$-1\le x\le 1$
Now, cosx is defined for all real values.
So, domain of cosx is R.
Domain of $f\left(x\right)\mathrm{is}\mathrm{R}\cap \left[-1,1\right]=\left[-1,1\right]$.