Answer
$\text{Not defined}$
Work Step by Step
Value of certain composite functions formula:
$f(f^{-1}(x)) = \cos{(\cos^{-1}{x})}= x \hspace{25pt} -1 \leq x \leq 1$
Note that $1.2 \text{ isn't in the interval } \left[-1,1 \right]$.
$\therefore \cos{(\cos^{-1}{(1.2)})} \text{ isn't defined}$.