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Theorem ceqex 3075
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 1765 . . 3  |-  ( x  =  A  ->  E. x  x  =  A )
2 isset 2969 . . 3  |-  ( A  e.  _V  <->  E. x  x  =  A )
31, 2sylibr 205 . 2  |-  ( x  =  A  ->  A  e.  _V )
4 eqeq2 2452 . . . 4  |-  ( y  =  A  ->  (
x  =  y  <->  x  =  A ) )
54anbi1d 687 . . . . . 6  |-  ( y  =  A  ->  (
( x  =  y  /\  ph )  <->  ( x  =  A  /\  ph )
) )
65exbidv 1638 . . . . 5  |-  ( y  =  A  ->  ( E. x ( x  =  y  /\  ph )  <->  E. x ( x  =  A  /\  ph )
) )
76bibi2d 311 . . . 4  |-  ( y  =  A  ->  (
( ph  <->  E. x ( x  =  y  /\  ph ) )  <->  ( ph  <->  E. x ( x  =  A  /\  ph )
) ) )
84, 7imbi12d 313 . . 3  |-  ( y  =  A  ->  (
( x  =  y  ->  ( ph  <->  E. x
( x  =  y  /\  ph ) ) )  <->  ( x  =  A  ->  ( ph  <->  E. x ( x  =  A  /\  ph )
) ) ) )
9 19.8a 1765 . . . . 5  |-  ( ( x  =  y  /\  ph )  ->  E. x
( x  =  y  /\  ph ) )
109ex 425 . . . 4  |-  ( x  =  y  ->  ( ph  ->  E. x ( x  =  y  /\  ph ) ) )
11 vex 2968 . . . . . 6  |-  y  e. 
_V
1211alexeq 3074 . . . . 5  |-  ( A. x ( x  =  y  ->  ph )  <->  E. x
( x  =  y  /\  ph ) )
13 sp 1766 . . . . . 6  |-  ( A. x ( x  =  y  ->  ph )  -> 
( x  =  y  ->  ph ) )
1413com12 30 . . . . 5  |-  ( x  =  y  ->  ( A. x ( x  =  y  ->  ph )  ->  ph ) )
1512, 14syl5bir 211 . . . 4  |-  ( x  =  y  ->  ( E. x ( x  =  y  /\  ph )  ->  ph ) )
1610, 15impbid 185 . . 3  |-  ( x  =  y  ->  ( ph 
<->  E. x ( x  =  y  /\  ph ) ) )
178, 16vtoclg 3020 . 2  |-  ( A  e.  _V  ->  (
x  =  A  -> 
( ph  <->  E. x ( x  =  A  /\  ph ) ) ) )
183, 17mpcom 35 1  |-  ( x  =  A  ->  ( ph 
<->  E. x ( x  =  A  /\  ph ) ) )
Colors of variables: wff set class
Syntax hints:    -> wi 4    <-> wb 178    /\ wa 360   A.wal 1550   E.wex 1551    = wceq 1654    e. wcel 1728   _Vcvv 2965
This theorem is referenced by:  ceqsexg  3076  sbc6g  3195
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1556  ax-5 1567  ax-17 1628  ax-9 1669  ax-8 1690  ax-6 1747  ax-7 1752  ax-11 1764  ax-12 1954  ax-ext 2424
This theorem depends on definitions:  df-bi 179  df-or 361  df-an 362  df-tru 1329  df-ex 1552  df-nf 1555  df-sb 1661  df-clab 2430  df-cleq 2436  df-clel 2439  df-nfc 2568  df-v 2967
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