--- /dev/null
+include "logic/equality.ma".
+
+(* Inclusion of: GRP023-2.p *)
+
+(* -------------------------------------------------------------------------- *)
+
+(* File : GRP023-2 : TPTP v3.7.0. Released v1.0.0. *)
+
+(* Domain : Group Theory *)
+
+(* Problem : The inverse of the identity is the identity *)
+
+(* Version : [MOW76] (equality) axioms : Augmented. *)
+
+(* English : *)
+
+(* Refs : [MOW76] McCharen et al. (1976), Problems and Experiments for a *)
+
+(* Source : [TPTP] *)
+
+(* Names : Established lemma [MOW76] *)
+
+(* Status : Unsatisfiable *)
+
+(* Rating : 0.00 v2.0.0 *)
+
+(* Syntax : Number of clauses : 6 ( 0 non-Horn; 6 unit; 1 RR) *)
+
+(* Number of atoms : 6 ( 6 equality) *)
+
+(* Maximal clause size : 1 ( 1 average) *)
+
+(* Number of predicates : 1 ( 0 propositional; 2-2 arity) *)
+
+(* Number of functors : 3 ( 1 constant; 0-2 arity) *)
+
+(* Number of variables : 7 ( 0 singleton) *)
+
+(* Maximal term depth : 3 ( 2 average) *)
+
+(* Comments : *)
+
+(* -------------------------------------------------------------------------- *)
+
+(* ----Include equality group theory axioms *)
+
+(* Inclusion of: Axioms/GRP004-0.ax *)
+
+(* -------------------------------------------------------------------------- *)
+
+(* File : GRP004-0 : TPTP v3.7.0. Released v1.0.0. *)
+
+(* Domain : Group Theory *)
+
+(* Axioms : Group theory (equality) axioms *)
+
+(* Version : [MOW76] (equality) axioms : *)
+
+(* Reduced > Complete. *)
+
+(* English : *)
+
+(* Refs : [MOW76] McCharen et al. (1976), Problems and Experiments for a *)
+
+(* : [Wos88] Wos (1988), Automated Reasoning - 33 Basic Research Pr *)
+
+(* Source : [ANL] *)
+
+(* Names : *)
+
+(* Status : *)
+
+(* Syntax : Number of clauses : 3 ( 0 non-Horn; 3 unit; 0 RR) *)
+
+(* Number of atoms : 3 ( 3 equality) *)
+
+(* Maximal clause size : 1 ( 1 average) *)
+
+(* Number of predicates : 1 ( 0 propositional; 2-2 arity) *)
+
+(* Number of functors : 3 ( 1 constant; 0-2 arity) *)
+
+(* Number of variables : 5 ( 0 singleton) *)
+
+(* Maximal term depth : 3 ( 2 average) *)
+
+(* Comments : [MOW76] also contains redundant right_identity and *)
+
+(* right_inverse axioms. *)
+
+(* : These axioms are also used in [Wos88] p.186, also with *)
+
+(* right_identity and right_inverse. *)
+
+(* -------------------------------------------------------------------------- *)
+
+(* ----For any x and y in the group x*y is also in the group. No clause *)
+
+(* ----is needed here since this is an instance of reflexivity *)
+
+(* ----There exists an identity element *)
+
+(* ----For any x in the group, there exists an element y such that x*y = y*x *)
+
+(* ----= identity. *)
+
+(* ----The operation '*' is associative *)
+
+(* -------------------------------------------------------------------------- *)
+
+(* -------------------------------------------------------------------------- *)
+
+(* ----Redundant two axioms *)
+ntheorem prove_inverse_of_id_is_id:
+ (∀Univ:Type.∀X:Univ.∀Y:Univ.∀Z:Univ.
+∀identity:Univ.
+∀inverse:∀_:Univ.Univ.
+∀multiply:∀_:Univ.∀_:Univ.Univ.
+∀H0:∀X:Univ.eq Univ (multiply X (inverse X)) identity.
+∀H1:∀X:Univ.eq Univ (multiply X identity) X.
+∀H2:∀X:Univ.∀Y:Univ.∀Z:Univ.eq Univ (multiply (multiply X Y) Z) (multiply X (multiply Y Z)).
+∀H3:∀X:Univ.eq Univ (multiply (inverse X) X) identity.
+∀H4:∀X:Univ.eq Univ (multiply identity X) X.eq Univ (inverse identity) identity)
+.
+#Univ ##.
+#X ##.
+#Y ##.
+#Z ##.
+#identity ##.
+#inverse ##.
+#multiply ##.
+#H0 ##.
+#H1 ##.
+#H2 ##.
+#H3 ##.
+#H4 ##.
+nauto by H0,H1,H2,H3,H4 ##;
+ntry (nassumption) ##;
+nqed.
+
+(* -------------------------------------------------------------------------- *)