proposition: Lemma mul_factor_wd : forall l l':R, 1 + (Rabs l + Rabs l') <> 0.
proof: Proof. intros; rewrite (Rplus_comm 1 (Rabs l + Rabs l')); apply Rplus_le_lt_0_neq_0. - cut (Rabs (l + l') <= Rabs l + Rabs l'). + cut (0 <= Rabs (l + l')). * exact (Rle_trans _ _ _). * exact (Rabs_pos (l + l')). + exact (Rabs_triang _ _). - exact Rlt_0_1. Qed.
imports: Rbase Rfunctions Lra