proposition: Lemma abs_ge0 x : 0 <= `|x|.
proof: Proof. by apply/leRq=> -[lt0x [a lt0a []]]; apply: ltc_trans lt0a; rewrite oppr0. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq order) mathcomp(ssralg ssrnum ssrint rat) fourcolor(real) Coq(Setoid Morphisms)