\[ \boxed { {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) +y \left ( x \right ) \cos \left ( x \right ) - \frac {1}{2}\,\sin \left ( 2\,x \right ) =0} \]
Mathematica: cpu = 0.022003 (sec), leaf count = 18 \[ \left \{\left \{y(x)\to c_1 e^{-\sin (x)}+\sin (x)-1\right \}\right \} \]
Maple: cpu = 0.078 (sec), leaf count = 15 \[ \left \{ y \left ( x \right ) =\sin \left ( x \right ) -1+{{\rm e}^{-\sin \left ( x \right ) }}{\it \_C1} \right \} \]
Sage: cpu = 0.008 (sec), leaf count = 0 \[ \left [{\left ({\left (\sin \left (x\right ) - 1\right )} e^{\sin \left (x\right )} + c\right )} e^{\left (-\sin \left (x\right )\right )}, \text {\texttt {linear}}\right ] \]