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Theorem r19.23vOLD 2913
Description: Obsolete proof of r19.23v 2912 as of 12-Jan-2020. (Contributed by NM, 31-Aug-1999.) (Proof modification is discouraged.) (New usage is discouraged.)
Assertion
Ref Expression
r19.23vOLD  |-  ( A. x  e.  A  ( ph  ->  ps )  <->  ( E. x  e.  A  ph  ->  ps ) )
Distinct variable group:    ps, x
Allowed substitution hints:    ph( x)    A( x)

Proof of Theorem r19.23vOLD
StepHypRef Expression
1 nfv 1754 . 2  |-  F/ x ps
21r19.23 2911 1  |-  ( A. x  e.  A  ( ph  ->  ps )  <->  ( E. x  e.  A  ph  ->  ps ) )
Colors of variables: wff setvar class
Syntax hints:    -> wi 4    <-> wb 187   A.wral 2782   E.wrex 2783
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1665  ax-4 1678  ax-5 1751  ax-6 1797  ax-7 1841  ax-10 1889  ax-12 1907
This theorem depends on definitions:  df-bi 188  df-an 372  df-ex 1660  df-nf 1664  df-ral 2787  df-rex 2788
This theorem is referenced by: (None)
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