proposition: Lemma Qball_Qmult_Q_l : Qball (proj1_sig d) (z * x) (z * y).
proof: Proof. intros. do 2 rewrite (Qmult_comm z). apply Qball_Qmult_Q_r. Qed.
imports: CoRN.metric2.Metric CoRN.metric2.Prelength CoRN.metric2.Classification CoRN.model.totalorder.QMinMax CoRN.model.totalorder.QposMinMax Coq.QArith.Qabs CoRN.metric2.UniformContinuity MathClasses.implementations.stdlib_rationals