proposition: Lemma derivableZ f (k : R) (x v : V) : derivable f x v -> derivable (k \*: f) x v.
proof: Proof. by move=> df; apply/cvg_ex; exists (k *: 'D_v f x); apply: der_scal. 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