On the number of limit cycles for perturbed pendulum equations

Armengol Gasull, Anna Geyer, Francesc Mañosas

We consider perturbed pendulum-like equations on the cylinder of the form $\ddot{x}+\sin (x)=\epsilon {\sum }_{s=0}^m{Q}_{n,s}(x){\dot{x}}^s$ where $Q_{n,s}$ are trigonometric…