proposition: Lemma pderivable_Ropp_xlnx : pderivable (fun y => - xlnx y) (fun x => 0 < x <= exp (- 1)).
proof: Proof. move=> x /= Hx. apply derivable_pt_opp. apply derivable_pt_xlnx. apply Hx. Defined.
imports: mathcomp(all_ssreflect ssralg ssrnum) mathcomp(Rstruct) Reals Lra ssrR realType_ext Reals_ext Ranalysis_ext logb convex