Solution
= Solution
For a first-order <linear ordinary differential equation> $y'+p(x)y=q(x)$, an <integrating factor> is $\exp(\int p(x)\,dx)$. Here $p(x)=\cot x$, so
$$
\mu(x)=\exp(\ln\sin x)=\boxed{\sin x.}
$$
The <sine> is positive on the specified interval, so this <integrating factor> never vanishes there. Any nonzero constant multiple is equally suitable.