  A method to generalize results from Riemannian Geometry to Finsler geometry
is presented. We use the method to generalize several results that involve only
metric conditions. Between them we show that the topology induced by the
Finsler structure is equivalent to the manifold topology, we provide a new
proof of the Hopf-Rinow theorem in Finsler geometry and we prove the existence
of the center of mass of a convex body when the non-symmetric distance function
comes from a non-reversible Finsler function.
