X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=helm%2Fsoftware%2Fmatita%2Flibrary%2Fnat%2Flog.ma;h=39d9b2ecdfae7ecc55209fd8e979581fd28dbbc9;hb=10f29fdd78ee089a9a94446207b543d33d6c851c;hp=53200b1613204457774133d2d9fdaad71527918e;hpb=1f136ddf1cf133efbf10b72b8800e0f8a93b6f68;p=helm.git

diff --git a/helm/software/matita/library/nat/log.ma b/helm/software/matita/library/nat/log.ma
index 53200b161..39d9b2ecd 100644
--- a/helm/software/matita/library/nat/log.ma
+++ b/helm/software/matita/library/nat/log.ma
@@ -159,6 +159,50 @@ cases n
   ]
 qed.
 
+theorem log_times_l: \forall p,n,m.O < n \to O < m \to S O < p \to 
+log p n+log p m \le log p (n*m) .
+intros.
+unfold log in ⊢ (? ? (% ? ?)).
+apply f_m_to_le_max
+  [elim H
+    [rewrite > log_SO
+      [simplify.
+       rewrite < plus_n_O.
+       apply le_log_n_n.
+       assumption
+      |assumption
+      ]
+    |elim H1
+      [rewrite > log_SO
+        [rewrite < plus_n_O.
+         rewrite < times_n_SO.
+         apply le_log_n_n.
+         assumption
+        |assumption
+        ]
+      |apply (trans_le ? (S n1 + S n2))
+        [apply le_plus;apply le_log_n_n;assumption
+        |simplify.
+         apply le_S_S.
+         rewrite < plus_n_Sm.
+         change in ⊢ (? % ?) with ((S n1)+n2).
+         rewrite > sym_plus.
+         apply le_plus_r.
+         change with (n1 < n1*S n2).
+         rewrite > times_n_SO in ⊢ (? % ?).
+         apply lt_times_r1
+          [assumption
+          |apply le_S_S.assumption
+          ]
+        ]
+      ]
+    ]
+  |apply le_to_leb_true.
+   rewrite > exp_plus_times.
+   apply le_times;apply le_exp_log;assumption
+  ]
+qed.
+
 theorem log_exp: \forall p,n,m.S O < p \to O < m \to
 log p ((exp p n)*m)=n+log p m.
 intros.
@@ -286,6 +330,30 @@ intros.elim H1
   [constructor 1
   |apply (trans_le ? ? ? H3);apply le_log_plus;assumption]
 qed.
+         
+theorem log_div: \forall p,n,m. S O < p \to O < m \to m \le n \to
+log p (n/m) \le log p n -log p m.
+intros.
+apply le_plus_to_minus_r.
+apply (trans_le ? (log p ((n/m)*m)))
+  [apply log_times_l
+    [apply le_times_to_le_div
+      [assumption
+      |rewrite < times_n_SO.
+       assumption
+      ]
+    |assumption
+    |assumption
+    ]
+  |apply le_log
+    [assumption
+    |rewrite > (div_mod n m) in ⊢ (? ? %)
+      [apply le_plus_n_r
+      |assumption
+      ]
+    ]
+  ]
+qed.
 
 theorem log_n_n: \forall n. S O < n \to log n n = S O.
 intros.