proposition: Lemma oprob_divRposxxy (x y : Rpos) : (0 < x / (x + y) < 1)%coqR.
proof: Proof. split; first by apply/divR_gt0. rewrite ltR_pdivr_mulr ?mul1R; last exact/RltP/addRpos_gt0. by rewrite ltR_addl. Qed.
imports: mathcomp(all_ssreflect) mathcomp(all_algebra vector reals normedtype) mathcomp(mathcomp_extra boolp) mathcomp(Rstruct) ssrR realType_ext Reals Lra mathcomp(lra)