proposition: Lemma UsetT E1 E2 : (E1 :|: E2) `*T = (E1 `*T) :|: (E2 `*T) :> {set A * B}.
proof: Proof. by apply/setP => -[a b]; rewrite !inE. Qed.
imports: mathcomp(all_ssreflect ssralg ssrnum matrix) mathcomp(Rstruct reals) Reals Lra ssrR Reals_ext realType_ext logb ssr_ext ssralg_ext bigop_ext fdist