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Theorem 19.23ht 1474
Description: Closed form of Theorem 19.23 of [Margaris] p. 90. (Contributed by NM, 7-Nov-2005.) (Revised by Mario Carneiro, 1-Feb-2015.)
Assertion
Ref Expression
19.23ht  |-  ( A. x ( ps  ->  A. x ps )  -> 
( A. x (
ph  ->  ps )  <->  ( E. x ph  ->  ps )
) )

Proof of Theorem 19.23ht
StepHypRef Expression
1 ax-ie2 1471 1  |-  ( A. x ( ps  ->  A. x ps )  -> 
( A. x (
ph  ->  ps )  <->  ( E. x ph  ->  ps )
) )
Colors of variables: wff set class
Syntax hints:    -> wi 4    <-> wb 104   A.wal 1330   E.wex 1469
This theorem was proved from axioms:  ax-ie2 1471
This theorem is referenced by:  19.23h  1475  exlimd2  1575  19.9ht  1621
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