Answer
$\color{blue}{s \approx 0.3887}$
Work Step by Step
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:
$s=\cos^{-1}{(\frac{1}{1.0806})} \color{blue}{\approx 0.3887}$
