proposition: Lemma is_cvg_seriesD f g : cvgn (series f) -> cvgn (series g) -> cvgn (series (f + g)).
proof: Proof. by move=> cf cg; rewrite seriesD; exact: is_cvgD. 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