proposition: Lemma A13_ (x y: A): dom(x·y) ≡ dom(x·dom y).
proof: Proof. by rewrite domE -dotA A11 dotA -domE. Qed.
imports: HB(structures) Coq(Setoid Morphisms) mathcomp(all_ssreflect) GraphTheory(edone preliminaries setoid_bigop structures pttdom)