Theorem exintrbi 1686

Description: Add/remove a conjunct in the scope of an existential quantifier. (Contributed by Raph Levien, 3-Jul-2006.)

Assertion

Ref	Expression
exintrbi	|- ( A. x ( ph -> ps ) -> ( E. x ph <-> E. x ( ph /\ ps ) ) )

Proof of Theorem exintrbi

Step	Hyp	Ref	Expression
1		pm4.71 393	. . 3 |- ( ( ph -> ps ) <-> ( ph <-> ( ph /\ ps ) ) )
2	1	albii 1523	. 2 |- ( A. x ( ph -> ps ) <-> A. x ( ph <-> ( ph /\ ps ) ) )
3		exbi 1657	. 2 |- ( A. x ( ph <-> ( ph /\ ps ) ) -> ( E. x ph <-> E. x ( ph /\ ps ) ) )
4	2, 3	sylbi 121	1 |- ( A. x ( ph -> ps ) -> ( E. x ph <-> E. x ( ph /\ ps ) ) )

This proof depends on syntax axioms:   -> wi 4   /\ wa 104   <-> wb 105   A.wal 1400   E.wex 1545

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-5 1500  ax-gen 1502  ax-ie1 1546  ax-ie2 1547  ax-4 1563  ax-ial 1587

This proof depends on definitions:  df-bi 117

This theorem is used by:  exintr  1687