Chapter 4 - Review Exercises - Page 646: 95

The exact value of the provided expression is $0$.

Let us assume $\theta ={{\cos }^{-1}}1$. Then, we have $\cos \theta =1$ We know that for the cosine function, the interval for the angle is $\left[ 0,\pi \right]$. So, the only angle that satisfies $\cos \theta =1$ is 0. Thus, $\theta =0$ and the exact value of the given expression is ${{\cos }^{-1}}1=0$