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Theorem pm11.7 26963
Description: Theorem *11.7 in [WhiteheadRussell] p. 166. (Contributed by Andrew Salmon, 24-May-2011.)
Assertion
Ref Expression
pm11.7  |-  ( E. x E. y (
ph  \/  ph )  <->  E. x E. y ph )

Proof of Theorem pm11.7
StepHypRef Expression
1 oridm 502 . 2  |-  ( (
ph  \/  ph )  <->  ph )
212exbii 1581 1  |-  ( E. x E. y (
ph  \/  ph )  <->  E. x E. y ph )
Colors of variables: wff set class
Syntax hints:    <-> wb 178    \/ wo 359   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-or 361  df-ex 1538
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