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Theorem pm10.253 26889
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 1570 . . 3  |-  ( A. x ph  <->  -.  E. x  -.  ph )
21bicomi 195 . 2  |-  ( -. 
E. x  -.  ph  <->  A. x ph )
32con1bii 323 1  |-  ( -. 
A. x ph  <->  E. x  -.  ph )
Colors of variables: wff set class
Syntax hints:   -. wn 5    <-> wb 178   A.wal 1532   E.wex 1537
This theorem was proved from axioms:  ax-1 7  ax-2 8  ax-3 9  ax-mp 10  ax-5 1533  ax-gen 1536
This theorem depends on definitions:  df-bi 179  df-ex 1538
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