\[ \boxed { x \left ( {\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left ( x \right ) +y \left ( x \right ) \right ) -\cos \left ( x \right ) =0} \]
Mathematica: cpu = 0.022503 (sec), leaf count = 41 \[ \left \{\left \{y(x)\to c_2 \sin (x)+c_1 \cos (x)+\frac {1}{2} (\text {Ci}(2 x) \sin (x)-\text {Si}(2 x) \cos (x)+\log (x) \sin (x))\right \}\right \} \]
Maple: cpu = 0.031 (sec), leaf count = 35 \[ \left \{ y \left ( x \right ) =\sin \left ( x \right ) {\it \_C2}+\cos \left ( x \right ) {\it \_C1}+{\frac {\sin \left ( x \right ) {\it Ci} \left ( 2\,x \right ) }{2}}+{\frac {\sin \left ( x \right ) \ln \left ( x \right ) }{2}}-{\frac {{\it Si} \left ( 2\,x \right ) \cos \left ( x \right ) }{2}} \right \} \]