\[ a x^3 \cos (x)+x y(x) y'(x)-y(x)^2=0 \] ✓ Mathematica : cpu = 0.148438 (sec), leaf count = 38
\[\left \{\left \{y(x)\to -x \sqrt {-2 a \sin (x)+c_1}\right \},\left \{y(x)\to x \sqrt {-2 a \sin (x)+c_1}\right \}\right \}\] ✓ Maple : cpu = 0.032 (sec), leaf count = 30
\[y \relax (x ) = \sqrt {-2 a \sin \relax (x )+c_{1}}\, x\]