Theorem incom | index | src |

theorem incom (A B: set): $ A i^i B == B i^i A $;
StepHypRefExpression
1 bitr
(x e. A i^i B <-> x e. A /\ x e. B) -> (x e. A /\ x e. B <-> x e. B i^i A) -> (x e. A i^i B <-> x e. B i^i A)
2 elin
x e. A i^i B <-> x e. A /\ x e. B
3 1, 2 ax_mp
(x e. A /\ x e. B <-> x e. B i^i A) -> (x e. A i^i B <-> x e. B i^i A)
4 bitr4
(x e. A /\ x e. B <-> x e. B /\ x e. A) -> (x e. B i^i A <-> x e. B /\ x e. A) -> (x e. A /\ x e. B <-> x e. B i^i A)
5 ancomb
x e. A /\ x e. B <-> x e. B /\ x e. A
6 4, 5 ax_mp
(x e. B i^i A <-> x e. B /\ x e. A) -> (x e. A /\ x e. B <-> x e. B i^i A)
7 elin
x e. B i^i A <-> x e. B /\ x e. A
8 6, 7 ax_mp
x e. A /\ x e. B <-> x e. B i^i A
9 3, 8 ax_mp
x e. A i^i B <-> x e. B i^i A
10 9 eqri
A i^i B == B i^i A

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp, itru), axs_pred_calc (ax_gen, ax_4, ax_5, ax_6, ax_7, ax_10, ax_11, ax_12), axs_set (elab, ax_8)