proposition: Lemma diffB (f g : V -> W) x : differentiable f x -> differentiable g x -> 'd (f - g) x = 'd f x \- 'd g x :> (V -> W).
proof: Proof. by move=> /differentiableP df /differentiableP dg; rewrite diff_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