proposition: Lemma inv_nexp_two : forall x : R, [--]x[^]2 [=] x[^]2.
proof: Proof. intro x. now apply inv_nexp_even; exists 1. 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)