proposition: Lemma is_cvgDlE f g : cvg (g @ F) -> cvg ((f + g) @ F) = cvg (f @ F).
proof: Proof. move=> g_cvg; rewrite propeqE; split; last by move=> /is_cvgD; apply. by move=> /is_cvgB /(_ g_cvg); rewrite addrK. Qed.
imports: HB(structures) mathcomp(all_ssreflect ssralg ssrint ssrnum finmap matrix) mathcomp(rat interval zmodp vector fieldext falgebra) mathcomp(mathcomp_extra boolp classical_sets functions) mathcomp(cardinality set_interval Rstruct) ereal reals signed topology prodnormedzmodule