Theorem 19.44

Description: Theorem 19.44 of Margaris p. 90. See 19.44v for a version requiring fewer axioms. (Contributed by NM, 12-Mar-1993)

	Ref	Expression
Hypothesis	19.44.1	|- F/ x ps
Assertion	19.44	|- ( E. x ( ph \/ ps ) <-> ( E. x ph \/ ps ) )

Proof

Step	Hyp	Ref	Expression
1		19.44.1	|- F/ x ps
2		19.43	|- ( E. x ( ph \/ ps ) <-> ( E. x ph \/ E. x ps ) )
3	1	19.9	|- ( E. x ps <-> ps )
4	3	orbi2i	|- ( ( E. x ph \/ E. x ps ) <-> ( E. x ph \/ ps ) )
5	2 4	bitri	|- ( E. x ( ph \/ ps ) <-> ( E. x ph \/ ps ) )