If $f:R \to R$ be given by $f(x) = \tan x$, then ${f^{ - 1}}(1)$ is

It is given that,, $f(x) = \tan x$

Let $y = \tan x \Rightarrow x = {\tan ^{ - 1}}y$

$\Rightarrow$ ${f^{ - 1}}(x) = {\tan ^{ - 1}}x \Rightarrow {f^{ - 1}}(1) = {\tan ^{ - 1}}1$

$\Rightarrow$ $= {\tan ^{ - 1}}\tan \frac{\pi }{4} = \frac{\pi }{4}$