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Theorem ceqex 2879
Description: Equality implies equivalence with substitution. (Contributed by NM, 2-Mar-1995.)
Assertion
Ref Expression
ceqex  |-  ( x  =  A  ->  ( ph 
<->  E. x ( x  =  A  /\  ph ) ) )
Distinct variable group:    x, A
Allowed substitution hint:    ph( x)

Proof of Theorem ceqex
Dummy variable  y is distinct from all other variables.
StepHypRef Expression
1 19.8a 1601 . . 3  |-  ( x  =  A  ->  E. x  x  =  A )
2 isset 2758 . . 3  |-  ( A  e.  _V  <->  E. x  x  =  A )
31, 2sylibr 134 . 2  |-  ( x  =  A  ->  A  e.  _V )
4 eqeq2 2199 . . . 4  |-  ( y  =  A  ->  (
x  =  y  <->  x  =  A ) )
54anbi1d 465 . . . . . 6  |-  ( y  =  A  ->  (
( x  =  y  /\  ph )  <->  ( x  =  A  /\  ph )
) )
65exbidv 1836 . . . . 5  |-  ( y  =  A  ->  ( E. x ( x  =  y  /\  ph )  <->  E. x ( x  =  A  /\  ph )
) )
76bibi2d 232 . . . 4  |-  ( y  =  A  ->  (
( ph  <->  E. x ( x  =  y  /\  ph ) )  <->  ( ph  <->  E. x ( x  =  A  /\  ph )
) ) )
84, 7imbi12d 234 . . 3  |-  ( y  =  A  ->  (
( x  =  y  ->  ( ph  <->  E. x
( x  =  y  /\  ph ) ) )  <->  ( x  =  A  ->  ( ph  <->  E. x ( x  =  A  /\  ph )
) ) ) )
9 19.8a 1601 . . . . 5  |-  ( ( x  =  y  /\  ph )  ->  E. x
( x  =  y  /\  ph ) )
109ex 115 . . . 4  |-  ( x  =  y  ->  ( ph  ->  E. x ( x  =  y  /\  ph ) ) )
11 vex 2755 . . . . . 6  |-  y  e. 
_V
1211alexeq 2878 . . . . 5  |-  ( A. x ( x  =  y  ->  ph )  <->  E. x
( x  =  y  /\  ph ) )
13 sp 1522 . . . . . 6  |-  ( A. x ( x  =  y  ->  ph )  -> 
( x  =  y  ->  ph ) )
1413com12 30 . . . . 5  |-  ( x  =  y  ->  ( A. x ( x  =  y  ->  ph )  ->  ph ) )
1512, 14biimtrrid 153 . . . 4  |-  ( x  =  y  ->  ( E. x ( x  =  y  /\  ph )  ->  ph ) )
1610, 15impbid 129 . . 3  |-  ( x  =  y  ->  ( ph 
<->  E. x ( x  =  y  /\  ph ) ) )
178, 16vtoclg 2812 . 2  |-  ( A  e.  _V  ->  (
x  =  A  -> 
( ph  <->  E. x ( x  =  A  /\  ph ) ) ) )
183, 17mpcom 36 1  |-  ( x  =  A  ->  ( ph 
<->  E. x ( x  =  A  /\  ph ) ) )
Colors of variables: wff set class
Syntax hints:    -> wi 4    /\ wa 104    <-> wb 105   A.wal 1362    = wceq 1364   E.wex 1503    e. wcel 2160   _Vcvv 2752
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-io 710  ax-5 1458  ax-7 1459  ax-gen 1460  ax-ie1 1504  ax-ie2 1505  ax-8 1515  ax-10 1516  ax-11 1517  ax-i12 1518  ax-bndl 1520  ax-4 1521  ax-17 1537  ax-i9 1541  ax-ial 1545  ax-i5r 1546  ax-ext 2171
This theorem depends on definitions:  df-bi 117  df-tru 1367  df-nf 1472  df-sb 1774  df-clab 2176  df-cleq 2182  df-clel 2185  df-nfc 2321  df-v 2754
This theorem is referenced by:  ceqsexg  2880  sbc6g  3002
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