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Theorem excom13 1760
Description: Swap 1st and 3rd existential quantifiers. (Contributed by NM, 9-Mar-1995.)
Assertion
Ref Expression
excom13  |-  ( E. x E. y E. z ph  <->  E. z E. y E. x ph )

Proof of Theorem excom13
StepHypRef Expression
1 excom 1758 . 2  |-  ( E. x E. y E. z ph  <->  E. y E. x E. z ph )
2 excom 1758 . . 3  |-  ( E. x E. z ph  <->  E. z E. x ph )
32exbii 1593 . 2  |-  ( E. y E. x E. z ph  <->  E. y E. z E. x ph )
4 excom 1758 . 2  |-  ( E. y E. z E. x ph  <->  E. z E. y E. x ph )
51, 3, 43bitri 264 1  |-  ( E. x E. y E. z ph  <->  E. z E. y E. x ph )
Colors of variables: wff set class
Syntax hints:    <-> wb 178   E.wex 1551
This theorem is referenced by:  exrot3  1761  exrot4  1762  euotd  4486  elfuns  25791
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1556  ax-5 1567  ax-7 1751
This theorem depends on definitions:  df-bi 179  df-ex 1552
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