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Theorem pm10.252 36346
Description: Theorem *10.252 in [WhiteheadRussell] p. 149. (Contributed by Andrew Salmon, 17-Jun-2011.) (New usage is discouraged.)
Assertion
Ref Expression
pm10.252  |-  ( -. 
E. x ph  <->  A. x  -.  ph )

Proof of Theorem pm10.252
StepHypRef Expression
1 df-ex 1660 . . 3  |-  ( E. x ph  <->  -.  A. x  -.  ph )
21bicomi 205 . 2  |-  ( -. 
A. x  -.  ph  <->  E. x ph )
32con1bii 332 1  |-  ( -. 
E. x ph  <->  A. x  -.  ph )
Colors of variables: wff setvar class
Syntax hints:   -. wn 3    <-> wb 187   A.wal 1435   E.wex 1659
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8
This theorem depends on definitions:  df-bi 188  df-ex 1660
This theorem is referenced by: (None)
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