proposition: Lemma Derive_div (f g : R -> R) (x : R) : ex_derive f x -> ex_derive g x -> g x <> 0 -> Derive (fun y => f y / g y) x = (Derive f x * g x - f x * Derive g x) / (g x) ^ 2.
proof: Proof. move => Hf Hg Hl. apply is_derive_unique. now apply is_derive_div ; try apply Derive_correct. Qed.
imports: Coq(Reals Psatz ssreflect) Rcomplements Rbar Lim_seq Iter Hierarchy Continuity Equiv