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Theorem cbvex2v 1960
Description: Rule used to change bound variables, using implicit substitution. (Contributed by NM, 26-Jul-1995.)
Hypothesis
Ref Expression
cbval2v.1  |-  ( ( x  =  z  /\  y  =  w )  ->  ( ph  <->  ps )
)
Assertion
Ref Expression
cbvex2v  |-  ( E. x E. y ph  <->  E. z E. w ps )
Distinct variable groups:    z, w, ph    x, y, ps    x, w    y, z
Allowed substitution hints:    ph( x, y)    ps( z, w)

Proof of Theorem cbvex2v
StepHypRef Expression
1 nfv 1609 . 2  |-  F/ z
ph
2 nfv 1609 . 2  |-  F/ w ph
3 nfv 1609 . 2  |-  F/ x ps
4 nfv 1609 . 2  |-  F/ y ps
5 cbval2v.1 . 2  |-  ( ( x  =  z  /\  y  =  w )  ->  ( ph  <->  ps )
)
61, 2, 3, 4, 5cbvex2 1958 1  |-  ( E. x E. y ph  <->  E. z E. w ps )
Colors of variables: wff set class
Syntax hints:    -> wi 4    <-> wb 176    /\ wa 358   E.wex 1531
This theorem is referenced by:  cbvex4v  1965  2mo  2234  2eu6  2241  th3qlem1  6780
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8  ax-gen 1536  ax-5 1547  ax-17 1606  ax-9 1644  ax-8 1661  ax-6 1715  ax-7 1720  ax-11 1727  ax-12 1878
This theorem depends on definitions:  df-bi 177  df-an 360  df-tru 1310  df-ex 1532  df-nf 1535
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