proposition: Lemma derivable_pt_in_ext : forall f g D x, f == g -> derivable_pt_in D f x -> derivable_pt_in D g x.
proof: Proof. intros f g D x Heq [l Hl] ; exists l ; eapply derivable_pt_lim_in_ext ; eassumption. Qed.
imports: Rbase Ranalysis Rinterval Rfunctions Rfunction_def Rfunction_facts Ranalysis_def Ranalysis_def_simpl Ranalysis_continuity MyRIneq MyR_dist Lra Tactics