Theorem bnj31

Description: First-order logic and set theory. (Contributed by Jonathan Ben-Naim, 3-Jun-2011) (New usage is discouraged.)

	Ref	Expression
Hypotheses	bnj31.1	|- ( ph -> E. x e. A ps )
	bnj31.2	|- ( ps -> ch )
Assertion	bnj31	|- ( ph -> E. x e. A ch )

Proof

Step	Hyp	Ref	Expression
1		bnj31.1	|- ( ph -> E. x e. A ps )
2		bnj31.2	|- ( ps -> ch )
3	2	reximi	|- ( E. x e. A ps -> E. x e. A ch )
4	1 3	syl	|- ( ph -> E. x e. A ch )