proposition: Lemma realEsqr x : (x \is real) = (0 <= x ^+ 2).
proof: Proof. by rewrite ger0_def normrX eqf_sqr -ger0_def -ler0_def. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)