#### Answer

$2.46052210868$

#### Work Step by Step

Make sure that the setting for angles is "radians".
$\sec^{-1}x$ is evaluated as $\displaystyle \cos^{-1}(\frac{1}{x}).$
Keys:
"shift" or "2nd function"
"cos"
numerical keypad: (-1.2871684)
"="
yields
$2.46052210868$