--- /dev/null
+(**************************************************************************)
+(* ___ *)
+(* ||M|| *)
+(* ||A|| A project by Andrea Asperti *)
+(* ||T|| *)
+(* ||I|| Developers: *)
+(* ||T|| The HELM team. *)
+(* ||A|| http://helm.cs.unibo.it *)
+(* \ / *)
+(* \ / This file is distributed under the terms of the *)
+(* v GNU General Public License Version 2 *)
+(* *)
+(**************************************************************************)
+
+include "ground_2/lib/star.ma".
+include "static_2/syntax/ext2.ma".
+
+(* EXTENSION TO BINDERS OF A RELATION FOR TERMS *****************************)
+
+(* Properties with transitive closure ***************************************)
+
+lemma ext2_tc_pair: ∀R,I,V1,V2. TC … R V1 V2 →
+ TC … (ext2 R) (BPair I V1) (BPair I V2).
+#R #I #V1 #V2 #H elim H -H -V2
+/3 width=3 by ext2_pair, step, inj/
+qed.
+
+lemma ext2_tc_inj: ∀R,I1,I2. ext2 R I1 I2 → ext2 (TC … R) I1 I2.
+#R #I1 #I2 * -I1 -I2
+/3 width=1 by ext2_unit, ext2_pair, inj/
+qed.
+
+(* Main properties with transitive closure **********************************)
+
+theorem ext2_tc_step: ∀R,I1,I. ext2 (TC … R) I1 I →
+ ∀I2. ext2 R I I2 → ext2 (TC … R) I1 I2.
+#R #I1 #I * -I1 -I
+[ #I #Z #H >(ext2_inv_unit_sn … H) -Z /2 width=1 by ext2_unit/
+| #I #V1 #V #HV1 #Z #H
+ elim (ext2_inv_pair_sn … H) -H #V2 #HV2 #H destruct
+ /3 width=3 by ext2_pair, step/
+]
+qed-.
+
+(* Advanced properties with transitive closure ******************************)
+
+lemma ext2_tc: ∀R,I1,I2. TC … (ext2 R) I1 I2 → ext2 (TC … R) I1 I2.
+#R #I1 #I2 #H elim H -I2
+/2 width=3 by ext2_tc_step, ext2_tc_inj/
+qed.
+
+(* Advanced inversion lemmas with transitive closure ************************)
+
+lemma ext2_inv_tc: ∀R,I1,I2. ext2 (TC … R) I1 I2 → TC … (ext2 R) I1 I2.
+#R #I1 #I2 * -I1 -I2
+/3 width=1 by ext2_tc_pair, ext2_unit, inj/
+qed-.