proposition: Lemma psos_r1b: forall x y:R, x - y == 0 -> x == y.
proof: Proof. intros x y H; setoid_replace x with ((x - y) + y); simpl; [setoid_rewrite H | idtac]; simpl. - cring. - cring. Qed.
imports: List Setoid BinPos BinList Znumtheory Morphisms Setoid Bool Algebra_syntax Ncring Ncring_initial Ncring_tac Integral_domain ZArith Lia