Chapter 3 - Radian Measure and the Unit Circle - Section 3.3 The Unit Circle and Circular Functions - 3.3 Exercises - Page 118: 59

$0.3887$

$\sec s=\frac{1}{\cos s}=1.0806$ $\frac{1}{\cos s}=1.0806$ can be rearranged to $\cos s=\frac{1}{1.0806}$ $\cos s=\frac{1}{1.0806}$ is further rearranged to $s=\cos^{-1} \frac{1}{1.0806}$ Ensuring that the calculator is in radians, we type $\cos^{-1} \frac{1}{1.0806}$ into the calculator and solve: $s=\cos^{-1} \frac{1}{1.0806}\approx0.3887$