fact: Definition RVn : {RV P -> 'rV[A]_n} := fun x => \row_(i < n) (X ``_ i) x.
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