Theorem exintr 1657

Description: Introduce a conjunct in the scope of an existential quantifier. (Contributed by NM, 11-Aug-1993.)

Assertion

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

Proof of Theorem exintr

Step	Hyp	Ref	Expression
1		exintrbi 1656	. 2 |- ( A. x ( ph -> ps ) -> ( E. x ph <-> E. x ( ph /\ ps ) ) )
2	1	biimpd 144	1 |- ( A. x ( ph -> ps ) -> ( E. x ph -> E. x ( ph /\ ps ) ) )

Syntax hints:   -> wi 4   /\ wa 104   A.wal 1371   E.wex 1515

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-5 1470  ax-gen 1472  ax-ie1 1516  ax-ie2 1517  ax-4 1533  ax-ial 1557

This theorem depends on definitions:  df-bi 117

This theorem is referenced by:  ceqsex  2810  r19.2m  3547  r19.2mOLD  3548