proposition: Lemma ImE z : 'Im z = 'i * (z^* - z) / 2%:R.
proof: Proof. by rewrite ['Im _]unlock. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)