\[
\boxed{
{x}^{2}{\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left( x \right) + \left( 2\,{x}^{2}\cot \left( x \right) +x \right) {\frac {\rm d}{{\rm d}x}}y \left( x \right) + \left( x\cot \left( x \right) +a \right) y \left( x \right) =0}
\]