proposition: Lemma is_cvg_npeseries_cond P N : (forall n, P n -> u_ n <= 0) -> cvgn (fun n => \sum_(N <= i < n | P i) u_ i).
proof: Proof. by move=> u_le0; apply: is_cvg_ereal_npos_natsum_cond => n _ /u_le0. 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