proposition: Lemma derivableB f g (x v : V) : derivable f x v -> derivable g x v -> derivable (f - g) x v.
proof: Proof. by move=> /derivableP df /derivableP dg. 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