(a)
$\sin{\left( 2\sin^{- 1}\sqrt{\frac{63}{65}} \right) = \sin\left( \sin^{- 1}{2\sqrt{\frac{63}{65}}\sqrt{1 - \frac{63}{65}}} \right)}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ = \sin{\left( \sin^{- 1}\frac{2\sqrt{126}}{65} \right) = \frac{2\sqrt{126}}{65}}$