proposition: Lemma invC_rect : {in real &, forall x y, (x + 'i * y)^-1 = (x - 'i * y) / (x ^+ 2 + y ^+ 2)}.
proof: Proof. by move=> x y Rx Ry; rewrite invC_Crect normC2_rect ?conj_Creal. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)