proposition: Lemma rational_arctan_mid_pos_prf a : 0 < a → - (1) < (a - 1) / (a + 1) < 1.
proof: Proof. split;(try apply Qlt_shift_div_l; try apply Qlt_shift_div_r; psatzl Q). Qed.
imports: CoRN.algebra.RSetoid CoRN.metric2.Metric CoRN.metric2.UniformContinuity CoRN.reals.fast.CRArith CoRN.reals.fast.CRIR CoRN.reals.Q_in_CReals CoRN.model.totalorder.QMinMax CoRN.reals.fast.CRarctan_small CoRN.reals.fast.CRpi CoRN.transc.MoreArcTan CoRN.reals.fast.ModulusDerivative CoRN.reals.fast.ContinuousCorrect CoRN.tactics.CornTac CoRN.stdlib_omissions.Q MathClasses.interfaces.abstract_algebra Coq.micromega.Psatz