$\frac{1}{2} \cos ^{-1}\left(\frac{9}{41}\right)=$ কত?

$\sin ^{-1}\left(\frac{40}{41}\right)$

$\sec ^{-1}\left(\frac{9}{41}\right)$

$\sin ^{-1}\left(\frac{40}{41}\right)$

$\tan ^{-1}\left(\frac{5}{4}\right)$