proposition: Lemma addRA x y z : x + (y + z) == x + y + z.
proof: Proof. exact: (Real.add_associative R). Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div order) mathcomp(ssralg ssrnum ssrint rat intdiv) Coq(Morphisms Setoid) fourcolor(real realsyntax)