% Mizar problem: t5_enumset1,enumset1,287,45 
fof(t5_enumset1, conjecture,  (! [A] :  (! [B] :  (! [C] :  (! [D] : k2_enumset1(A, B, C, D)=k2_xboole_0(k2_tarski(A, B), k2_tarski(C, D))) ) ) ) ).
fof(commutativity_k2_tarski, axiom,  (! [A, B] : k2_tarski(A, B)=k2_tarski(B, A)) ).
fof(commutativity_k2_xboole_0, axiom,  (! [A, B] : k2_xboole_0(A, B)=k2_xboole_0(B, A)) ).
fof(idempotence_k2_xboole_0, axiom,  (! [A, B] : k2_xboole_0(A, A)=A) ).
fof(dt_k2_enumset1, axiom, $true).
fof(dt_k2_tarski, axiom, $true).
fof(dt_k2_xboole_0, axiom, $true).
fof(l13_enumset1, axiom,  (! [A] :  (! [B] :  (! [C] :  (! [D] : k2_enumset1(A, B, C, D)=k2_xboole_0(k2_tarski(A, B), k2_tarski(C, D))) ) ) ) ).
