(a) Find the Maclaurin series for \(\sin ^{-1} x\) up to and including the term in \(x^{3}\).
(b) Deduce an approximation to \(\int_{0}^{\frac{1}{5}} \frac{1}{\sqrt{1-u^{2}}} \mathrm{~d} u\), giving your answer as a fraction.