Theorem 19.9t 1622

Description: A closed version of 19.9 1624. (Contributed by NM, 5-Aug-1993.) (Revised by Mario Carneiro, 24-Sep-2016.) (Proof shortended by Wolf Lammen, 30-Dec-2017.)

Assertion

Ref	Expression
19.9t	|- ( F/ x ph -> ( E. x ph <-> ph ) )

Proof of Theorem 19.9t

Step	Hyp	Ref	Expression
1		df-nf 1438	. . 3 |- ( F/ x ph <-> A. x ( ph -> A. x ph ) )
2		19.9ht 1621	. . 3 |- ( A. x ( ph -> A. x ph ) -> ( E. x ph -> ph ) )
3	1, 2	sylbi 120	. 2 |- ( F/ x ph -> ( E. x ph -> ph ) )
4		19.8a 1570	. 2 |- ( ph -> E. x ph )
5	3, 4	impbid1 141	1 |- ( F/ x ph -> ( E. x ph <-> ph ) )

Syntax hints:   -> wi 4   <-> wb 104   A.wal 1330   F/wnf 1437   E.wex 1469

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-gen 1426  ax-ie1 1470  ax-ie2 1471  ax-4 1488

This theorem depends on definitions:  df-bi 116  df-nf 1438

This theorem is referenced by:  19.9d  1640  19.23t  1656  spimt  1715  exdistrfor  1773  sbequi  1812  sbft  1821  vtoclegft  2761  copsexg  4174