proposition: Lemma shift_minus_less' : forall x y z : R, x [<] y[+]z -> x[-]y [<] z.
proof: Proof. intros. apply shift_minus_less. astepr (y[+]z). assumption. Qed.
imports: CoRN.tactics.FieldReflection CoRN.tactics.Rational CoRN.algebra.CSetoids Coq(Lia)