\[ \boxed { \left ( x\sin \left ( y \left ( x \right ) \right ) -1 \right ) {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) +\cos \left ( y \left ( x \right ) \right ) =0} \]
Mathematica: cpu = 0.064008 (sec), leaf count = 145 \[ \left \{\left \{y(x)\to -\cos ^{-1}\left (\frac {c_1 x-\sqrt {c_1^2-x^2+1}}{c_1^2+1}\right )\right \},\left \{y(x)\to \cos ^{-1}\left (\frac {c_1 x-\sqrt {c_1^2-x^2+1}}{c_1^2+1}\right )\right \},\left \{y(x)\to -\cos ^{-1}\left (\frac {\sqrt {c_1^2-x^2+1}+c_1 x}{c_1^2+1}\right )\right \},\left \{y(x)\to \cos ^{-1}\left (\frac {\sqrt {c_1^2-x^2+1}+c_1 x}{c_1^2+1}\right )\right \}\right \} \]
Maple: cpu = 0.047 (sec), leaf count = 115 \[ \left \{ y \left ( x \right ) =\arctan \left ( {\frac {{\it \_C1}}{{{\it \_C1}}^{2}+1} \left ( -{\it \_C1}\,x+\sqrt {{{\it \_C1}}^{2}-{x}^{2}+1} \right ) }+x,-{\frac {1}{{{\it \_C1}}^{2}+1} \left ( -{\it \_C1}\,x+ \sqrt {{{\it \_C1}}^{2}-{x}^{2}+1} \right ) } \right ) ,y \left ( x \right ) =\arctan \left ( -{\frac {{\it \_C1}}{{{\it \_C1}}^{2}+1} \left ( {\it \_C1}\,x+\sqrt {{{\it \_C1}}^{2}-{x}^{2}+1} \right ) }+x,{ \frac {1}{{{\it \_C1}}^{2}+1} \left ( {\it \_C1}\,x+\sqrt {{{\it \_C1}} ^{2}-{x}^{2}+1} \right ) } \right ) \right \} \]