The domain of the given function is the set of all real numbers.
Work Step by Step
The denominator of a rational function cannot be $0$, hence $x^2+1$ should not be $0$. However, the value of $x^2+1$ will never be equal to zero since the value of $x^2$ is always non-negative for all real numbers. Thus, the domain of the given function is the set of all real numbers.