Answer
$1.3607651$ radian
Work Step by Step
Ensuring that the calculator is in radian mode, we enter $\sec^{-1} (4.7963825)$ as $\cos^{-1} (\frac{1}{4.7963825})$ into the calculator and solve:
$y=\cos^{-1} (\frac{1}{4.7963825})\approx1.3607651$ radian
