\[ \boxed { \left ( \left ( {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) \right ) ^{2}+1 \right ) \left ( \sin \left ( x{\frac {\rm d}{{\rm d}x}}y \left ( x \right ) -y \left ( x \right ) \right ) \right ) ^{2}-1=0} \]
Mathematica: cpu = 0.040505 (sec), leaf count = 59 \[ \left \{\left \{y(x)\to c_1 x-\frac {1}{2} \cos ^{-1}\left (\frac {c_1^2-1}{c_1^2+1}\right )\right \},\left \{y(x)\to c_1 x+\frac {1}{2} \cos ^{-1}\left (\frac {c_1^2-1}{c_1^2+1}\right )\right \}\right \} \]
Maple: cpu = 0.358 (sec), leaf count = 147 \[ \left \{ y \left ( x \right ) ={\it \_C1}\,x-\arcsin \left ( {\frac {1}{ \sqrt {{{\it \_C1}}^{2}+1}}} \right ) ,y \left ( x \right ) ={\it \_C1}\, x+\arcsin \left ( {\frac {1}{\sqrt {{{\it \_C1}}^{2}+1}}} \right ) ,y \left ( x \right ) =-\sqrt {1-x}\sqrt {{x}^{-1}}x-\arcsin \left ( \sqrt {{x}^{-1}}x \right ) ,y \left ( x \right ) =\sqrt {1-x}\sqrt {{x}^{-1}}x+ \arcsin \left ( \sqrt {{x}^{-1}}x \right ) ,y \left ( x \right ) =-\sqrt { 1+x}\sqrt {-{x}^{-1}}x-\arcsin \left ( \sqrt {-{x}^{-1}}x \right ) ,y \left ( x \right ) =\sqrt {1+x}\sqrt {-{x}^{-1}}x+\arcsin \left ( \sqrt {-{x}^{-1}}x \right ) \right \} \]