Theorem eliminable3a

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	eliminable3a	|- ( { x | ph } e. y <-> E. z ( z = { x | ph } /\ z e. y ) )

Proof

Step	Hyp	Ref	Expression
1		dfclel	|- ( { x | ph } e. y <-> E. z ( z = { x | ph } /\ z e. y ) )