proposition: Lemma sqrp_eq1 x : 0 <= x -> (x ^+ 2 == 1) = (x == 1).
proof: Proof. by move/pexpr_eq1->. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)