proposition: Lemma E_scaler_RV k : `E (X `*cst k) = `E X * k.
proof: Proof. by rewrite big_distrl /=; apply: eq_bigr => i Hi; rewrite mulRAC. 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