Some sufficient conditions for the intersection with the vertical isocline in the Liénard plane Original Research Article

In this work we study the problem of whether all trajectories of the system View the MathML sourceẋ=y−F(x) and View the MathML sourceẏ=−g(x) cross the vertical isocline, which is very important for the existence of periodic solutions and oscillation theory. Sufficient conditions are given for all trajectories to cross the vertical isocline.