proposition: Lemma derivableM f g (x v : V) : derivable f x v -> derivable g x v -> derivable (f * g) x v.
proof: Proof. move=> df dg; apply/cvg_ex; exists (f x *: 'D_v g x + g x *: 'D_v f x). exact: der_mult. Qed.
imports: HB(structures) mathcomp(all_ssreflect ssralg ssrnum matrix interval) mathcomp(mathcomp_extra boolp classical_sets functions) reals signed topology prodnormedzmodule normedtype landau forms