proposition: Lemma Im_div x y : 'Im (x / y) = ('Re y * 'Im x - 'Re x * 'Im y) / `|y| ^+ 2.
proof: Proof. by rewrite ImM ImV ReV mulrA [X in _ + X]mulrAC -mulrDl mulrN addrC. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)