Question (Really struggling

It is given that, for non-negative integers n,

$l_n=\int_{0}^{1/2\pi} sin^nx dx$

Show that $l_n=\frac{n-1}{n}l_{n-2}$ for any $n\geq 2$

Explain why $l_{2n+1} < l_{2n-1}$

It is given that $l_{2n+1}< l_{2n}<l_{2n-1}$ Take $n=5$ to find an intervel within which value of $\pi$ lies.