proposition: Lemma ring_dist_minus : forall x y z : R, x[*] (y[-]z) [=] x[*]y[-]x[*]z.
proof: Proof. intros x y z. unfold cg_minus in |- *. Step_final (x[*]y[+]x[*] [--]z). Qed.
imports: CoRN.tactics.CornTac CoRN.algebra.CSums CoRN.algebra.CAbMonoids Coq.Sorting.Permutation CoRN.util.SetoidPermutation Coq.Setoids.Setoid Coq.Classes.Morphisms Coq(Lia)