simplify.reflexivity.
qed.
+theorem lt_to_eq_mod:\forall n,m:nat. n < m \to n \mod m = n.
+intros.
+apply div_mod_spec_to_eq2 n m (n/m) (n \mod m) O n.
+apply div_mod_spec_div_mod.
+apply le_to_lt_to_lt O n m.apply le_O_n.assumption.
+constructor 1.
+assumption.reflexivity.
+qed.
(* injectivity *)
theorem injective_times_r: \forall n:nat.injective nat nat (\lambda m:nat.(S n)*m).