Answer
$$\frac{\pi}{6}$$
Work Step by Step
Let $\sec^{-1}\frac{2}{\sqrt 3}=x $, then we have
$$\sec x =\frac{2}{\sqrt 3}\Longrightarrow x=\frac{\pi}{6}.$$
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.