proposition: Lemma ex_derive_Reals_1 (f : R -> R) (x : R) : derivable_pt f x -> ex_derive f x.
proof: Proof. case => l Hf. exists l. now apply is_derive_Reals. Qed.
imports: Coq(Reals Psatz ssreflect) Rcomplements Rbar Lim_seq Iter Hierarchy Continuity Equiv