proposition: Lemma oppC_rect x y : - (x + 'i * y) = - x + 'i * (- y).
proof: Proof. by rewrite mulrN -opprD. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)