Theorem: SetTheory.inter_comm (SetTheory/Basic.lean)

State before:
V : Type u_1
inst✝ : Zermelo V
x y z : V
⊢ x ∩ y = y ∩ x
Tactic:
ext
State after:
case h
V : Type u_1
inst✝ : Zermelo V
x y z z✝ : V
⊢ z✝ ∈ x ∩ y ↔ z✝ ∈ y ∩ x

State before:
case h
V : Type u_1
inst✝ : Zermelo V
x y z z✝ : V
⊢ z✝ ∈ x ∩ y ↔ z✝ ∈ y ∩ x
Tactic:
aesop
State after:
no goals