proposition: Lemma derivable_pt_in_inv: forall (D : R -> Prop) f x, D x -> f x <> 0 -> derivable_pt_in D f x -> derivable_pt_in D (/ f)%F x.
proof: Proof. intros D f x Dx Hneq [] ; eexists ; eapply derivable_pt_lim_in_inv ; eassumption. Qed.
imports: Rbase Ranalysis Rinterval Rfunctions Rfunction_def Rfunction_facts Ranalysis_def Ranalysis_def_simpl Ranalysis_continuity MyRIneq MyR_dist Lra Tactics