proposition: Lemma ex_derive_Reals_0 (f : R -> R) (x : R) : ex_derive f x -> derivable_pt f x.
proof: Proof. move => Hf. apply Derive_correct in Hf. apply is_derive_Reals in Hf. by exists (Derive f x). Qed.
imports: Coq(Reals Psatz ssreflect) Rcomplements Rbar Lim_seq Iter Hierarchy Continuity Equiv