theorem injective_S : \forall n,m:nat.
(eq nat (S n) (S m)) \to (eq nat n m).
intros;
-rewrite > pred_Sn n;
-rewrite > pred_Sn m;
+rewrite > pred_Sn;
+rewrite > pred_Sn m.
apply f_equal; assumption.
qed.
\forall n,m:nat. eq nat (plus n (times n m)) (times n (S m)).
intros.elim n.simplify.reflexivity.
simplify.apply f_equal.rewrite < H.
-transitivity (plus (plus e m) (times e m)).symmetry.
-apply assoc_plus.transitivity (plus (plus m e) (times e m)).
+transitivity (plus (plus e1 m) (times e1 m)).symmetry.
+apply assoc_plus.transitivity (plus (plus m e1) (times e1 m)).
apply f_equal2.
apply sym_plus.reflexivity.apply assoc_plus.
qed.
theorem sym_times :
\forall n,m:nat. eq nat (times n m) (times m n).
intros.elim n.simplify.apply times_n_O.
-simplify.rewrite < sym_eq ? ? ? H.apply times_n_Sm.
+simplify.rewrite > H.apply times_n_Sm.
qed.
let rec minus n m \def
theorem le_Sn_n : \forall n:nat. Not (le (S n) n).
intros.elim n.apply le_Sn_O.simplify.intros.
-cut le (S e) e.apply H.assumption.apply le_S_n.assumption.
+cut le (S e1) e1.apply H.assumption.apply le_S_n.assumption.
qed.
theorem le_antisym : \forall n,m:nat. (le n m) \to (le m n) \to (eq nat n m).