proposition: Lemma sqrtCK x : sqrtC x ^+ 2 = x.
proof: Proof. exact: rootCK. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)