proposition: Lemma Rmul_0_l x : 0 * x == 0.
proof: Proof. setoid_replace (0*x) with ((0+1)*x + -x). - now rewrite (Radd_0_l Rth), (Rmul_1_l Rth), (Ropp_def Rth). - rewrite (Rdistr_l Rth), (Rmul_1_l Rth). rewrite <- (Radd_assoc Rth), (Ropp_def Rth). now rewrite (Radd_comm Rth), (Radd_0_l Rth). Qed.
imports: Setoid Morphisms BinPos BinNat