proposition: Lemma derive_Rball_inv: forall f c r x pr pr', f x <> 0 -> derive_Rball c r (/ f)%F pr x = (- derive_Rball c r f pr' x) / (f x) ^ 2.
proof: Proof. intros ; unfold derive_Rball ; destruct (in_Rball_dec c r x) as [x_in | x_nin] ; [apply derive_pt_Rball_inv ; assumption | rewrite Ropp_0, Rdiv_0_l ; reflexivity]. Qed.
imports: Rbase Ranalysis Rinterval Rfunctions Rfunction_def Rfunction_facts Ranalysis_def Ranalysis_def_simpl Ranalysis_continuity MyRIneq MyR_dist Lra Tactics