Parameters in Duffing

Dear Developer,

In the duffing equation, getting started part, the damping parameter in the text is ```\gamma``` but in the code it is ```\eta```, also the damping is multiplied by ```x^2```which is not in the equation, am I right? 
 
<img width="897" height="247" alt="Image" src="https://github.com/user-attachments/assets/98d16cad-1a45-4a22-8a5f-228c53f60c3b" />