\[ y''(x)-\cot (x) y'(x)+y(x) \sin ^2(x)=0 \] ✓ Mathematica : cpu = 0.0306345 (sec), leaf count = 19
\[\{\{y(x)\to c_1 \cos (\cos (x))-c_2 \sin (\cos (x))\}\}\] ✓ Maple : cpu = 0.151 (sec), leaf count = 15
\[\{y \left (x \right ) = c_{1} \sin \left (\cos \left (x \right )\right )+c_{2} \cos \left (\cos \left (x \right )\right )\}\]