\[ y'(x)-\tan (x y(x))=0 \] ✓ Mathematica : cpu = 0.429712 (sec), leaf count = 69
\[\text {Solve}\left [\frac {1}{2} \sqrt {\frac {\pi }{2}} e^{\frac {x^2}{2}} \left (\text {erfi}\left (\frac {y(x)-i x}{\sqrt {2}}\right )+\text {erfi}\left (\frac {y(x)+i x}{\sqrt {2}}\right )\right )=c_1 e^{\frac {x^2}{2}},y(x)\right ]\] ✓ Maple : cpu = 0.356 (sec), leaf count = 44
\[\left \{y \left (x \right ) = -i \RootOf \left (c_{1} \sqrt {2}-\sqrt {\pi }\, \erf \left (\frac {\sqrt {2}\, \left (\textit {\_Z} +x \right )}{2}\right )-\sqrt {\pi }\, \erf \left (\frac {\left (\textit {\_Z} -x \right ) \sqrt {2}}{2}\right )\right )\right \}\]