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Theorem pm10.253 27660
Description: Theorem *10.253 in [WhiteheadRussell] p. 149. (Contributed by Andrew Salmon, 17-Jun-2011.)
Assertion
Ref Expression
pm10.253  |-  ( -. 
A. x ph  <->  E. x  -.  ph )

Proof of Theorem pm10.253
StepHypRef Expression
1 alex 1562 . . 3  |-  ( A. x ph  <->  -.  E. x  -.  ph )
21bicomi 193 . 2  |-  ( -. 
E. x  -.  ph  <->  A. x ph )
32con1bii 321 1  |-  ( -. 
A. x ph  <->  E. x  -.  ph )
Colors of variables: wff set class
Syntax hints:   -. wn 3    <-> wb 176   A.wal 1530   E.wex 1531
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8  ax-gen 1536  ax-5 1547
This theorem depends on definitions:  df-bi 177  df-ex 1532
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