Theorem exbi 1495

Description: Theorem 19.18 of [Margaris] p. 90. (Contributed by NM, 5-Aug-1993.)

Assertion

Ref	Expression
exbi	|- ( A. x ( ph <-> ps ) -> ( E. x ph <-> E. x ps ) )

Proof of Theorem exbi

Step	Hyp	Ref	Expression
1		bi1 111	. . . 4 |- ( ( ph <-> ps ) -> ( ph -> ps ) )
2	1	alimi 1344	. . 3 |- ( A. x ( ph <-> ps ) -> A. x ( ph -> ps ) )
3		exim 1490	. . 3 |- ( A. x ( ph -> ps ) -> ( E. x ph -> E. x ps ) )
4	2, 3	syl 14	. 2 |- ( A. x ( ph <-> ps ) -> ( E. x ph -> E. x ps ) )
5		bi2 121	. . . 4 |- ( ( ph <-> ps ) -> ( ps -> ph ) )
6	5	alimi 1344	. . 3 |- ( A. x ( ph <-> ps ) -> A. x ( ps -> ph ) )
7		exim 1490	. . 3 |- ( A. x ( ps -> ph ) -> ( E. x ps -> E. x ph ) )
8	6, 7	syl 14	. 2 |- ( A. x ( ph <-> ps ) -> ( E. x ps -> E. x ph ) )
9	4, 8	impbid 120	1 |- ( A. x ( ph <-> ps ) -> ( E. x ph <-> E. x ps ) )

Syntax hints:   -> wi 4   <-> 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:  exbii  1496  exbidh  1505  exintrbi  1524  19.19  1556  rexrnmpt  5310