Question: Write the value of $\sin ^{-1}\left(\sin \frac{3 \pi}{5}\right)$
Solution:
$\sin ^{-1}\left(\sin \frac{3 \pi}{5}\right)=\sin ^{-1}\left[\sin \left(\pi-\frac{2 \pi}{5}\right)\right]$
$=\sin ^{-1}\left(\sin \frac{2 \pi}{5}\right)$
$=\frac{2 \pi}{5}$
