$11\mathrm{.}3\mathrm{.}9($a$)$ For ${\displaystyle \underset{-1}{\overset{1}{}}}[f(x){]}^{2}dx=2{\displaystyle \underset{n=0}{\overset{}{}}}(4n+3)[\frac{(2n-1)!!}{(2n+2)!!}{]}^2.$