Theorem eliminable2a

Description: A theorem used to prove the base case of the Eliminability Theorem (see section comment). (Contributed by BJ, 19-Oct-2019) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Assertion	eliminable2a	⊢ ( 𝑥 = { 𝑦 ∣ 𝜑 } ↔ ∀ 𝑧 ( 𝑧 ∈ 𝑥 ↔ 𝑧 ∈ { 𝑦 ∣ 𝜑 } ) )

Proof

Step	Hyp	Ref	Expression
1		dfcleq	⊢ ( 𝑥 = { 𝑦 ∣ 𝜑 } ↔ ∀ 𝑧 ( 𝑧 ∈ 𝑥 ↔ 𝑧 ∈ { 𝑦 ∣ 𝜑 } ) )