Answer
$ f(x)=9^{\tan x}$ is defined and continuous on its domain $ x\in R; \ x\neq \frac{(2n+1)\pi}{2}$, $ n $ is an integer.
Work Step by Step
Since $\tan x=\frac{\sin x}{\cos x}$ is defined and continuous on all $ x\in R $ such that $ x\neq \frac{(2n+1)\pi}{2}$, $ n $ is an integer then $ f(x)=9^{\tan x}$ is defined and continuous on its domain $ x\in R; \ x\neq \frac{(2n+1)\pi}{2}$, $ n $ is integer.
