\[ \boxed { \left ( {\frac {{\rm d}^{3}}{{\rm d}{x}^{3}}}y \left ( x \right ) \right ) \sin \left ( x \right ) + \left ( 2\,\cos \left ( x \right ) +1 \right ) {\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left ( x \right ) -\sin \left ( x \right ) {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) -\cos \left ( x \right ) =0} \]
Mathematica: cpu = 0.494563 (sec), leaf count = 72 \[ \left \{\left \{y(x)\to \frac {\sin \left (\frac {x}{2}\right ) \left (\sqrt {2} \left (c_2 x \sin \left (\frac {x}{2}\right )+\cos \left (\frac {x}{2}\right ) \left (c_2 \log (2 (\cos (x)+1))+2 c_1\right )\right )-2 \cos \left (\frac {x}{2}\right ) \sin ^{-1}(\cos (x))\right )}{\cos (x)-1}+c_3\right \}\right \} \]
Maple: cpu = 0.078 (sec), leaf count = 68 \[ \left \{ y \left ( x \right ) ={\frac {{\it \_C1}}{-1+\cos \left ( x \right ) } \left ( \ln \left ( \sin \left ( x \right ) \right ) \sin \left ( x \right ) -\ln \left ( -{\frac {-1+\cos \left ( x \right ) }{ \sin \left ( x \right ) }} \right ) \sin \left ( x \right ) -\cos \left ( x \right ) x+x \right ) }+{\it \_C2}+{\frac {\sin \left ( x \right ) {\it \_C3}}{-1+\cos \left ( x \right ) }}+{\frac {-\cos \left ( x \right ) x+ \sin \left ( x \right ) -x}{\sin \left ( x \right ) }} \right \} \]