$$\big(A+B\tanh (Cy+D)\big)\frac{\mathrm dy}{\mathrm dx}+y=P\cos(\omega x),$$ where $A$, $B$, $C$, $D$ and $\omega$ are constant.
I am really looking for an analytical solution to this differential equation. But I really don't know where to start. Can someone please help? Thank you.