proposition: Lemma amul_ge0 {x y} : `|x|*|y| >= 0.
proof: Proof. by case=> a _ /abs_ge0; rewrite ltcE mul0r ltxx. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq order) mathcomp(ssralg ssrnum ssrint rat) fourcolor(real) Coq(Setoid Morphisms)