\[ \boxed { f \left ( x \right ) {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) +g \left ( x \right ) {\it tg} \left ( y \left ( x \right ) \right ) +h \left ( x \right ) =0} \]
Mathematica: cpu = 20.512605 (sec), leaf count = 22 \[ \text {DSolve}\left [f(x) y'(x)+g(x) \text {tg}(y(x))+h(x)=0,y(x),x\right ] \]
Maple: cpu = 0.172 (sec), leaf count = 0 \[ \text {could not solve} \]