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Theorem axsep2 3950
Description: A less restrictive version of the Separation Scheme ax-sep 3949, where variables  x and  z can both appear free in the wff  ph, which can therefore be thought of as  ph ( x ,  z ). This version was derived from the more restrictive ax-sep 3949 with no additional set theory axioms. (Contributed by NM, 10-Dec-2006.) (Proof shortened by Mario Carneiro, 17-Nov-2016.)
Assertion
Ref Expression
axsep2  |-  E. y A. x ( x  e.  y  <->  ( x  e.  z  /\  ph )
)
Distinct variable groups:    x, y, z    ph, y
Allowed substitution hints:    ph( x, z)

Proof of Theorem axsep2
Dummy variable  w is distinct from all other variables.
StepHypRef Expression
1 eleq2 2151 . . . . . . 7  |-  ( w  =  z  ->  (
x  e.  w  <->  x  e.  z ) )
21anbi1d 453 . . . . . 6  |-  ( w  =  z  ->  (
( x  e.  w  /\  ( x  e.  z  /\  ph ) )  <-> 
( x  e.  z  /\  ( x  e.  z  /\  ph )
) ) )
3 anabs5 540 . . . . . 6  |-  ( ( x  e.  z  /\  ( x  e.  z  /\  ph ) )  <->  ( x  e.  z  /\  ph )
)
42, 3syl6bb 194 . . . . 5  |-  ( w  =  z  ->  (
( x  e.  w  /\  ( x  e.  z  /\  ph ) )  <-> 
( x  e.  z  /\  ph ) ) )
54bibi2d 230 . . . 4  |-  ( w  =  z  ->  (
( x  e.  y  <-> 
( x  e.  w  /\  ( x  e.  z  /\  ph ) ) )  <->  ( x  e.  y  <->  ( x  e.  z  /\  ph )
) ) )
65albidv 1752 . . 3  |-  ( w  =  z  ->  ( A. x ( x  e.  y  <->  ( x  e.  w  /\  ( x  e.  z  /\  ph ) ) )  <->  A. x
( x  e.  y  <-> 
( x  e.  z  /\  ph ) ) ) )
76exbidv 1753 . 2  |-  ( w  =  z  ->  ( E. y A. x ( x  e.  y  <->  ( x  e.  w  /\  (
x  e.  z  /\  ph ) ) )  <->  E. y A. x ( x  e.  y  <->  ( x  e.  z  /\  ph )
) ) )
8 ax-sep 3949 . 2  |-  E. y A. x ( x  e.  y  <->  ( x  e.  w  /\  ( x  e.  z  /\  ph ) ) )
97, 8chvarv 1860 1  |-  E. y A. x ( x  e.  y  <->  ( x  e.  z  /\  ph )
)
Colors of variables: wff set class
Syntax hints:    /\ wa 102    <-> wb 103   A.wal 1287   E.wex 1426
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 104  ax-ia2 105  ax-ia3 106  ax-5 1381  ax-gen 1383  ax-ie1 1427  ax-ie2 1428  ax-4 1445  ax-17 1464  ax-i9 1468  ax-ial 1472  ax-ext 2070  ax-sep 3949
This theorem depends on definitions:  df-bi 115  df-nf 1395  df-cleq 2081  df-clel 2084
This theorem is referenced by: (None)
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