Theorem exintrbi 1524

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		pm4.71 369	. . 3 |- ( ( ph -> ps ) <-> ( ph <-> ( ph /\ ps ) ) )
2	1	albii 1359	. 2 |- ( A. x ( ph -> ps ) <-> A. x ( ph <-> ( ph /\ ps ) ) )
3		exbi 1495	. 2 |- ( A. x ( ph <-> ( ph /\ ps ) ) -> ( E. x ph <-> E. x ( ph /\ ps ) ) )
4	2, 3	sylbi 114	1 |- ( A. x ( ph -> ps ) -> ( E. x ph <-> E. x ( ph /\ ps ) ) )

Syntax hints:   -> wi 4   /\ wa 97   <-> wb 98   A.wal 1241   E.wex 1381

This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 99  ax-ia2 100  ax-ia3 101  ax-5 1336  ax-gen 1338  ax-ie1 1382  ax-ie2 1383  ax-4 1400  ax-ial 1427

This theorem depends on definitions:  df-bi 110

This theorem is referenced by:  exintr  1525