\[ \boxed { \left ( {x}^{2}+1 \right ) {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) +x\sin \left ( y \left ( x \right ) \right ) \cos \left ( y \left ( x \right ) \right ) -x \left ( {x}^{2}+1 \right ) \left ( \cos \left ( y \left ( x \right ) \right ) \right ) ^{2}=0} \]
Mathematica: cpu = 0.242031 (sec), leaf count = 40 \[ \left \{\left \{y(x)\to \tan ^{-1}\left (\frac {-6 c_1 \sqrt {x^2+1}+x^4+2 x^2+1}{3 \left (x^2+1\right )}\right )\right \}\right \} \]
Maple: cpu = 0.530 (sec), leaf count = 25 \[ \left \{ y \left ( x \right ) =\arctan \left ( {\frac {1}{3} \left ( \left ( {x}^{2}+1 \right ) ^{{\frac {3}{2}}}+3\,{\it \_C1} \right ) { \frac {1}{\sqrt {{x}^{2}+1}}}} \right ) \right \} \]