2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/138365We construct, for a homogeneous Lagrangian of arbitrary order in two independent variables, a differential 2-form with the property that it is closed precisely when the Lagrangian is null. This is similar to the property of the `fundamental Lepage equivalent' associated with first-order Lagrangians defined on jets of sections of a fibred manifold.Differential Geometry58E99,;49F99text