Answer
$\sqrt {1-u^2}$
Work Step by Step
Let $sin^{-1}(u)=t$, we have $sin(t)=u$, thus $cos(t)=\sqrt {1-sin^2(t)}=\sqrt {1-u^2}$
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.