Answer
The exact value of the provided expression is $\frac{\pi }{2}$.
Work Step by Step
Let $\theta ={{\sin }^{-1}}1$. Then, we have
$\sin \theta =1$
For the sine function, the interval for the angle is $\left[ -\frac{\pi }{2},\frac{\pi }{2} \right]$. So, the only angle that satisfies $\sin \theta =1$ is $\frac{\pi }{2}$.
Thus, $\theta =\frac{\pi }{2}$ and the exact value of given expression is
${{\sin }^{-1}}1=\frac{\pi }{2}$
