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Theorem axextndbi 24719
Description: axextnd 8303 as a biconditional. (Contributed by Scott Fenton, 14-Dec-2010.)
Assertion
Ref Expression
axextndbi  |-  E. z
( x  =  y  <-> 
( z  e.  x  <->  z  e.  y ) )

Proof of Theorem axextndbi
StepHypRef Expression
1 axextnd 8303 . . 3  |-  E. z
( ( z  e.  x  <->  z  e.  y )  ->  x  =  y )
2 elequ2 1715 . . . . 5  |-  ( x  =  y  ->  (
z  e.  x  <->  z  e.  y ) )
32jctl 525 . . . 4  |-  ( ( ( z  e.  x  <->  z  e.  y )  ->  x  =  y )  ->  ( ( x  =  y  ->  ( z  e.  x  <->  z  e.  y ) )  /\  (
( z  e.  x  <->  z  e.  y )  ->  x  =  y )
) )
43eximi 1576 . . 3  |-  ( E. z ( ( z  e.  x  <->  z  e.  y )  ->  x  =  y )  ->  E. z ( ( x  =  y  ->  (
z  e.  x  <->  z  e.  y ) )  /\  ( ( z  e.  x  <->  z  e.  y )  ->  x  =  y ) ) )
51, 4ax-mp 8 . 2  |-  E. z
( ( x  =  y  ->  ( z  e.  x  <->  z  e.  y ) )  /\  (
( z  e.  x  <->  z  e.  y )  ->  x  =  y )
)
6 dfbi2 609 . . 3  |-  ( ( x  =  y  <->  ( z  e.  x  <->  z  e.  y ) )  <->  ( (
x  =  y  -> 
( z  e.  x  <->  z  e.  y ) )  /\  ( ( z  e.  x  <->  z  e.  y )  ->  x  =  y ) ) )
76exbii 1582 . 2  |-  ( E. z ( x  =  y  <->  ( z  e.  x  <->  z  e.  y ) )  <->  E. z
( ( x  =  y  ->  ( z  e.  x  <->  z  e.  y ) )  /\  (
( z  e.  x  <->  z  e.  y )  ->  x  =  y )
) )
85, 7mpbir 200 1  |-  E. z
( x  =  y  <-> 
( z  e.  x  <->  z  e.  y ) )
Colors of variables: wff set class
Syntax hints:    -> wi 4    <-> wb 176    /\ wa 358   E.wex 1541    = wceq 1642    e. wcel 1710
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8  ax-gen 1546  ax-5 1557  ax-17 1616  ax-9 1654  ax-8 1675  ax-13 1712  ax-14 1714  ax-6 1729  ax-7 1734  ax-11 1746  ax-12 1930  ax-ext 2339
This theorem depends on definitions:  df-bi 177  df-an 360  df-tru 1319  df-ex 1542  df-nf 1545  df-sb 1649  df-cleq 2351  df-clel 2354  df-nfc 2483
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