2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/169825We prove the result stated in the title; it is equivalent to the existence of a regular point of the sub-Riemannian exponential mapping. We also prove that the metric is analytic on an open everywhere dense subset in the case of a complete real-analytic sub-Riemannian manifold.Differential GeometryOptimization and Controltext