proposition: Lemma sqr_norm_eq1 x : (x ^+ 2 == 1) = (`|x| == 1).
proof: Proof. by rewrite sqrf_eq1 eqr_norml ler01 andbT. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)