2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/61311The geodesics for a sub-Riemannian metric on a three-dimensional contact manifold $M$ form a 1-parameter family of curves along each contact direction. However, a collection of such contact curves on $M$, locally equivalent to the solutions of a fourth-order ODE, are the geodesics of a sub-Riemannian metric only if a sequence of invariants vanish. The first of these, which was earlier identified by Fels, determines if the differential equation is variational. The next two determine if there is a well-defined metric on $M$ and if the given paths are its geodesics.13 pagesDifferential GeometryOptimization and Control53C17;49N45 (Primary) 34A26;53A55 (Secondary)text