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Theorem zfauscl 4334
Description: Separation Scheme (Aussonderung) using a class variable. To derive this from ax-sep 4332, we invoke the Axiom of Extensionality (indirectly via vtocl 3008), which is needed for the justification of class variable notation.

If we omit the requirement that  y not occur in  ph, we can derive a contradiction, as notzfaus 4376 shows. (Contributed by NM, 5-Aug-1993.)

Hypothesis
Ref Expression
zfauscl.1  |-  A  e. 
_V
Assertion
Ref Expression
zfauscl  |-  E. y A. x ( x  e.  y  <->  ( x  e.  A  /\  ph )
)
Distinct variable groups:    x, y, A    ph, y
Allowed substitution hint:    ph( x)

Proof of Theorem zfauscl
Dummy variable  z is distinct from all other variables.
StepHypRef Expression
1 zfauscl.1 . 2  |-  A  e. 
_V
2 eleq2 2499 . . . . . 6  |-  ( z  =  A  ->  (
x  e.  z  <->  x  e.  A ) )
32anbi1d 687 . . . . 5  |-  ( z  =  A  ->  (
( x  e.  z  /\  ph )  <->  ( x  e.  A  /\  ph )
) )
43bibi2d 311 . . . 4  |-  ( z  =  A  ->  (
( x  e.  y  <-> 
( x  e.  z  /\  ph ) )  <-> 
( x  e.  y  <-> 
( x  e.  A  /\  ph ) ) ) )
54albidv 1636 . . 3  |-  ( z  =  A  ->  ( A. x ( x  e.  y  <->  ( x  e.  z  /\  ph )
)  <->  A. x ( x  e.  y  <->  ( x  e.  A  /\  ph )
) ) )
65exbidv 1637 . 2  |-  ( z  =  A  ->  ( E. y A. x ( x  e.  y  <->  ( x  e.  z  /\  ph )
)  <->  E. y A. x
( x  e.  y  <-> 
( x  e.  A  /\  ph ) ) ) )
7 ax-sep 4332 . 2  |-  E. y A. x ( x  e.  y  <->  ( x  e.  z  /\  ph )
)
81, 6, 7vtocl 3008 1  |-  E. y A. x ( x  e.  y  <->  ( x  e.  A  /\  ph )
)
Colors of variables: wff set class
Syntax hints:    <-> wb 178    /\ wa 360   A.wal 1550   E.wex 1551    = wceq 1653    e. wcel 1726   _Vcvv 2958
This theorem is referenced by:  inex1  4346
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8  ax-gen 1556  ax-5 1567  ax-17 1627  ax-9 1667  ax-8 1688  ax-6 1745  ax-11 1762  ax-ext 2419  ax-sep 4332
This theorem depends on definitions:  df-bi 179  df-an 362  df-ex 1552  df-nf 1555  df-sb 1660  df-clab 2425  df-cleq 2431  df-clel 2434  df-v 2960
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