proposition: Lemma deriveB f g (x v : V) : derivable f x v -> derivable g x v -> 'D_v (f - g) x = 'D_v f x - 'D_v g x.
proof: Proof. by move=> /derivableP df /derivableP dg; rewrite derive_val. 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