Question: Write the value of $\cos ^{-1}\left(\cos \frac{14 \pi}{3}\right)$
Solution:
$\cos ^{-1}\left(\cos \frac{14 \pi}{3}\right)=\cos ^{-1}\left[\cos \left(4 \pi+\frac{2 \pi}{3}\right)\right]$
$=\cos ^{-1}\left(\cos \frac{2 \pi}{3}\right)$
$=\frac{2 \pi}{3}$
