Theorem prid1

Description: An unordered pair contains its first member. Part of Theorem 7.6 of Quine p. 49. (Contributed by NM, 24-Jun-1993)

	Ref	Expression
Hypothesis	prid1.1	|- A e. _V
Assertion	prid1	|- A e. { A , B }

Proof

Step	Hyp	Ref	Expression
1		prid1.1	|- A e. _V
2		prid1g	|- ( A e. _V -> A e. { A , B } )
3	1 2	ax-mp	|- A e. { A , B }