## Precalculus (6th Edition)

$\color{blue}{s \approx 0.3887}$
RECALL: $\sec{\theta}=\dfrac{1}{\cos{\theta}}$ and $\cos{\theta}=\dfrac{1}{\sec{\theta}}$ With $\sec{s}=1.0806$, then $\cos{s}=\dfrac{1}{1.0806}$ To find $s$, use the inverse cosine function of a calculator in radian mode, then round-off the answer to four decimal places to obtain: $s=\cos^{-1}{(\frac{1}{1.0806})} \color{blue}{\approx 0.3887}$