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ZF (ZERMELO-FRAENKEL) SET THEORY
ZF Set Theory - start with the Axiom of Extensionality
The intersection of a class
elintabg
Metamath Proof Explorer
Description: Two ways of saying a set is an element of the intersection of a class.
(Contributed by NM , 30-Aug-1993) Put in closed form. (Revised by RP , 13-Aug-2020)
Ref
Expression
Assertion
elintabg
⊢ A ∈ V → A ∈ ⋂ x | φ ↔ ∀ x φ → A ∈ x
Proof
Step
Hyp
Ref
Expression
1
elintg
⊢ A ∈ V → A ∈ ⋂ x | φ ↔ ∀ y ∈ x | φ A ∈ y
2
eleq2w
⊢ y = x → A ∈ y ↔ A ∈ x
3
2
ralab2
⊢ ∀ y ∈ x | φ A ∈ y ↔ ∀ x φ → A ∈ x
4
1 3
bitrdi
⊢ A ∈ V → A ∈ ⋂ x | φ ↔ ∀ x φ → A ∈ x