Find the exact value of the expression whenever it is defined.
(a) $\sin \left[\sin ^{-1} \frac{5}{13}-\cos ^{-1}\left(-\frac{3}{5}\right)\right]$
(b) $\cos \left(\sin ^{-1} \frac{4}{5}+\tan ^{-1} \frac{3}{4}\right)$
(c) $\tan \left(\cos ^{-1} \frac{1}{2}-\sin ^{-1} \frac{1}{2}\right)$