Answer
$1.23$
Work Step by Step
We know that $\sec {a}=\dfrac{1}{\cos{(a)}}$.
This can also be written as: $\sec^{-1} {a}=\cos^{-1} (\dfrac{1}{a})$
In order to get the answer in radians, we want to set the calculator in radians mode, and use the inverse cosine function (round off the result to two decimal places) to obtain:
$\sec^{-1} (3) =\cos^{-1} (\dfrac{1}{3})=1.2310 \approx 1.23$
The equation $cos\theta=\frac{1}{3}$ implies that that $\theta$ lies in quadrant I and the angle of the final answer also lies in quadrant I, so we do not need to modify the result.
