proposition: Lemma derivable_pt_in_const : forall D k x, derivable_pt_in D (fun _ => k) x.
proof: Proof. intros ; eexists ; eapply derivable_pt_lim_in_const. Qed.
imports: Rbase Ranalysis Rinterval Rfunctions Rfunction_def Rfunction_facts Ranalysis_def Ranalysis_def_simpl Ranalysis_continuity MyRIneq MyR_dist Lra Tactics