proposition: Lemma Rleb_norm_add x y : Rleb (Rabs (x + y)) (Rabs x + Rabs y).
proof: Proof. by apply/RlebP/Rabs_triang. Qed.
imports: Rdefinitions Raxioms RIneq Rbasic_fun Zwf Epsilon FunctionalExtensionality Ranalysis1 Rsqrt_def Rtrigo1 Reals mathcomp(all_ssreflect ssralg poly mxpoly ssrnum) HB(structures)