proposition: Lemma poweR12_sqrt x : 0 <= x -> x `^ 2^-1 = sqrte x.
proof: Proof. move: x => [x|_|//]; last by rewrite poweRyr. by rewrite lee_fin => x0 /=; rewrite powR12_sqrt. Qed.
imports: mathcomp(all_ssreflect ssralg ssrint ssrnum matrix) mathcomp(interval rat) mathcomp(boolp classical_sets functions) mathcomp(mathcomp_extra) reals ereal signed topology normedtype landau sequences derive realfun itv convex