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Theorem pm11.61 27254
Description: Theorem *11.61 in [WhiteheadRussell] p. 166. (Contributed by Andrew Salmon, 24-May-2011.)
Assertion
Ref Expression
pm11.61  |-  ( E. y A. x (
ph  ->  ps )  ->  A. x ( ph  ->  E. y ps ) )
Distinct variable group:    ph, y
Allowed substitution hints:    ph( x)    ps( x, y)

Proof of Theorem pm11.61
StepHypRef Expression
1 19.12 1859 . 2  |-  ( E. y A. x (
ph  ->  ps )  ->  A. x E. y (
ph  ->  ps ) )
2 19.37v 1911 . . . 4  |-  ( E. y ( ph  ->  ps )  <->  ( ph  ->  E. y ps ) )
32biimpi 187 . . 3  |-  ( E. y ( ph  ->  ps )  ->  ( ph  ->  E. y ps )
)
43alimi 1565 . 2  |-  ( A. x E. y ( ph  ->  ps )  ->  A. x
( ph  ->  E. y ps ) )
51, 4syl 16 1  |-  ( E. y A. x (
ph  ->  ps )  ->  A. x ( ph  ->  E. y ps ) )
Colors of variables: wff set class
Syntax hints:    -> wi 4   A.wal 1546   E.wex 1547
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8  ax-gen 1552  ax-5 1563  ax-17 1623  ax-9 1661  ax-8 1682  ax-6 1736  ax-7 1741  ax-11 1753
This theorem depends on definitions:  df-bi 178  df-an 361  df-ex 1548  df-nf 1551
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