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Theorem 2nalexn 1699
Description: Part of theorem *11.5 in [WhiteheadRussell] p. 164. (Contributed by Andrew Salmon, 24-May-2011.)
Assertion
Ref Expression
2nalexn  |-  ( -. 
A. x A. y ph 
<->  E. x E. y  -.  ph )

Proof of Theorem 2nalexn
StepHypRef Expression
1 df-ex 1663 . . 3  |-  ( E. x E. y  -. 
ph 
<->  -.  A. x  -.  E. y  -.  ph )
2 alex 1697 . . . 4  |-  ( A. y ph  <->  -.  E. y  -.  ph )
32albii 1690 . . 3  |-  ( A. x A. y ph  <->  A. x  -.  E. y  -.  ph )
41, 3xchbinxr 313 . 2  |-  ( E. x E. y  -. 
ph 
<->  -.  A. x A. y ph )
54bicomi 206 1  |-  ( -. 
A. x A. y ph 
<->  E. x E. y  -.  ph )
Colors of variables: wff setvar class
Syntax hints:   -. wn 3    <-> wb 188   A.wal 1441   E.wex 1662
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1668  ax-4 1681
This theorem depends on definitions:  df-bi 189  df-ex 1663
This theorem is referenced by:  spc2gv  3136  hashfun  12606  spc2d  28100  pm11.52  36730  2exanali  36731
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