intro. apply witness n O O.apply times_n_O.
qed.
+theorem divides_n_n: \forall n:nat. n \divides n.
+intro. apply witness n n (S O).apply times_n_SO.
+qed.
+
theorem divides_SO_n: \forall n:nat. (S O) \divides n.
intro. apply witness (S O) n n. simplify.apply plus_n_O.
qed.
variant trans_divides: \forall n,m,p.
n \divides m \to m \divides p \to n \divides p \def transitive_divides.
+theorem eq_mod_to_divides:\forall n,m,p. O< p \to
+mod n p = mod m p \to divides p (n-m).
+intros.
+cut n \le m \or \not n \le m.
+elim Hcut.
+cut n-m=O.
+rewrite > Hcut1.
+apply witness p O O.
+apply times_n_O.
+apply eq_minus_n_m_O.
+assumption.
+apply witness p (n-m) ((div n p)-(div m p)).
+rewrite > distr_times_minus.
+rewrite > sym_times.
+rewrite > sym_times p.
+cut (div n p)*p = n - (mod n p).
+rewrite > Hcut1.
+rewrite > eq_minus_minus_minus_plus.
+rewrite > sym_plus.
+rewrite > H1.
+rewrite < div_mod.reflexivity.
+assumption.
+apply sym_eq.
+apply plus_to_minus.
+rewrite > sym_plus.
+apply div_mod.
+assumption.
+apply decidable_le n m.
+qed.
+
(* divides le *)
theorem divides_to_le : \forall n,m. O < m \to n \divides m \to n \le m.
intros. elim H1.rewrite > H2.cut O < n2.
qed.
(* divides and pi *)
-theorem divides_f_pi_f : \forall f:nat \to nat.\forall n,i:nat.
-i < n \to f i \divides pi n f.
-intros 3.elim n.apply False_ind.apply not_le_Sn_O i H.
+theorem divides_f_pi_f : \forall f:nat \to nat.\forall n,m,i:nat.
+m \le i \to i \le n+m \to f i \divides pi n f m.
+intros 5.elim n.simplify.
+cut i = m.rewrite < Hcut.apply divides_n_n.
+apply antisymmetric_le.assumption.assumption.
simplify.
-apply le_n_Sm_elim (S i) n1 H1.
-intro.
-apply transitive_divides ? (pi n1 f).
-apply H.simplify.apply le_S_S_to_le. assumption.
-apply witness ? ? (f n1).apply sym_times.
-intro.cut i = n1.
-rewrite > Hcut.
-apply witness ? ? (pi n1 f).reflexivity.
-apply inj_S.assumption.
+cut i < S n1+m \lor i = S n1 + m.
+elim Hcut.
+apply transitive_divides ? (pi n1 f m).
+apply H1.apply le_S_S_to_le. assumption.
+apply witness ? ? (f (S n1+m)).apply sym_times.
+rewrite > H3.
+apply witness ? ? (pi n1 f m).reflexivity.
+apply le_to_or_lt_eq.assumption.
qed.
+(*
theorem mod_S_pi: \forall f:nat \to nat.\forall n,i:nat.
i < n \to (S O) < (f i) \to (S (pi n f)) \mod (f i) = (S O).
intros.cut (pi n f) \mod (f i) = O.
apply divides_to_mod_O.apply trans_lt O (S O).apply le_n (S O).assumption.
apply divides_f_pi_f.assumption.
qed.
+*)
(* divides and fact *)
theorem divides_fact : \forall n,i:nat.
cut (S(S O)) = (S(S m1)) - m1.
rewrite > Hcut.
apply le_min_aux.
-apply sym_eq.apply plus_to_minus.apply le_S.apply le_n_Sn.
+apply sym_eq.apply plus_to_minus.
rewrite < sym_plus.simplify.reflexivity.
qed.
cut (S(S O)) = (S(S m1)-m1).
rewrite < Hcut.exact H1.
apply sym_eq. apply plus_to_minus.
-apply le_S.apply le_n_Sn.
rewrite < sym_plus.simplify.reflexivity.
exact H2.
qed.