proposition: Lemma ex_derive_n_opp (f : R -> R) (n : nat) (x : R) : ex_derive_n f n x -> ex_derive_n (fun x => -f x) n x.
proof: Proof. case: n x => [ | n] /= x Hf. by []. apply ex_derive_opp in Hf. apply: ex_derive_ext Hf. move => y ; by rewrite Derive_n_opp. Qed.
imports: Coq(Reals Psatz ssreflect) Rcomplements Rbar Lim_seq Iter Hierarchy Continuity Equiv