proposition: Lemma sub_eseries_geq m n : (m <= n)%N -> eseries m \is a fin_num -> eseries n - eseries m = \sum_(m <= k < n) u_ k.
proof: Proof. by move=> /subnK<- emfin; rewrite eseries_addn addeAC subee// add0e. Qed.
imports: mathcomp(all_ssreflect ssralg ssrint ssrnum matrix) mathcomp(interval rat) mathcomp(mathcomp_extra boolp classical_sets functions) mathcomp(set_interval) reals ereal signed topology normedtype landau