proposition: Lemma nroot_I_nexp_aux : forall n, Nat.Odd n -> {m : nat | n * n = 4 * m + 1}.
proof: Proof. intros n H; destruct (even_or_odd_plus n) as [m [Hm | ->]]. - exfalso; apply (Nat.Even_Odd_False n); [| exact H]. exists m; rewrite Hm; ring. - exists (m * m + m); ring. Qed.
imports: CoRN.complex.CComplex Coq.Arith.Wf_nat Coq.setoid_ring.ArithRing