proposition: Lemma derive_pt_eq_1 : forall f (x l:R) (pr:derivable_pt f x), derive_pt f x pr = l -> derivable_pt_lim f x l.
proof: Proof. intros; elim (derive_pt_eq f x l pr); intros. apply (H0 H). Qed.
imports: Rbase Rfunctions Rlimit Rderiv