Chapter 1.7, Problem 26ES

From Exercise 1.5.58, under the assumptions that $f$ is an invertible function, $f(0)=0,f$ is continuous at 0, and lim $x\to 0(f(x)/x)$ exists, then

$\underset{x\to 0}{\lim }\frac{x}{f^{-1}(x)}=\underset{x\to 0}{\lim }\frac{f(x)}{x}$

Apply this result, if needed, to find the limit.

$\text{ 26}\text{. }\underset{x\to 0}{\lim }\frac{{\tan }^{-1}x}{x}$