Answer
$(0, +\infty)$
Work Step by Step
Recall:
(1) The function $f(x)=\sqrt{x}$ is defined only when $x\ge0$.
(2) The function $f(x) = \ln{x}$ is defined only when $x\gt0$.
Thus, the given function is defined only when $\ln{x}$ is greater than or equal to zero.
However, since $f(x)=\ln{x}$ is only defined when $ x \gt 0$, then, the given function is defined when $x \gt0$.