proposition: Lemma ltr0_sqrtr a : a < 0 -> sqrt a = 0.
proof: Proof. by move=> /ltW; apply: ler0_sqrtr. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)