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Theorem br2ndeq 24131
Description: Uniqueness condition for binary relationship over the  2nd relationship. (Contributed by Scott Fenton, 11-Apr-2014.) (Proof shortened by Mario Carneiro, 3-May-2015.)
Hypotheses
Ref Expression
br2ndeq.1  |-  A  e. 
_V
br2ndeq.2  |-  B  e. 
_V
br2ndeq.3  |-  C  e. 
_V
Assertion
Ref Expression
br2ndeq  |-  ( <. A ,  B >. 2nd C  <->  C  =  B
)

Proof of Theorem br2ndeq
StepHypRef Expression
1 br2ndeq.1 . . . 4  |-  A  e. 
_V
2 br2ndeq.2 . . . 4  |-  B  e. 
_V
31, 2op2nd 6129 . . 3  |-  ( 2nd `  <. A ,  B >. )  =  B
43eqeq1i 2290 . 2  |-  ( ( 2nd `  <. A ,  B >. )  =  C  <-> 
B  =  C )
5 fo2nd 6140 . . . 4  |-  2nd : _V -onto-> _V
6 fofn 5453 . . . 4  |-  ( 2nd
: _V -onto-> _V  ->  2nd 
Fn  _V )
75, 6ax-mp 8 . . 3  |-  2nd  Fn  _V
8 opex 4237 . . 3  |-  <. A ,  B >.  e.  _V
9 fnbrfvb 5563 . . 3  |-  ( ( 2nd  Fn  _V  /\  <. A ,  B >.  e. 
_V )  ->  (
( 2nd `  <. A ,  B >. )  =  C  <->  <. A ,  B >. 2nd C ) )
107, 8, 9mp2an 653 . 2  |-  ( ( 2nd `  <. A ,  B >. )  =  C  <->  <. A ,  B >. 2nd C )
11 eqcom 2285 . 2  |-  ( B  =  C  <->  C  =  B )
124, 10, 113bitr3i 266 1  |-  ( <. A ,  B >. 2nd C  <->  C  =  B
)
Colors of variables: wff set class
Syntax hints:    <-> wb 176    = wceq 1623    e. wcel 1684   _Vcvv 2788   <.cop 3643   class class class wbr 4023    Fn wfn 5250   -onto->wfo 5253   ` cfv 5255   2ndc2nd 6121
This theorem is referenced by:  dfrn5  24133  brtxp  24420  brpprod  24425  elfuns  24454  brimg  24476  brcup  24478  brcap  24479  brrestrict  24487
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8  ax-gen 1533  ax-5 1544  ax-17 1603  ax-9 1635  ax-8 1643  ax-13 1686  ax-14 1688  ax-6 1703  ax-7 1708  ax-11 1715  ax-12 1866  ax-ext 2264  ax-sep 4141  ax-nul 4149  ax-pow 4188  ax-pr 4214  ax-un 4512
This theorem depends on definitions:  df-bi 177  df-or 359  df-an 360  df-3an 936  df-tru 1310  df-ex 1529  df-nf 1532  df-sb 1630  df-eu 2147  df-mo 2148  df-clab 2270  df-cleq 2276  df-clel 2279  df-nfc 2408  df-ne 2448  df-ral 2548  df-rex 2549  df-rab 2552  df-v 2790  df-sbc 2992  df-dif 3155  df-un 3157  df-in 3159  df-ss 3166  df-nul 3456  df-if 3566  df-sn 3646  df-pr 3647  df-op 3649  df-uni 3828  df-br 4024  df-opab 4078  df-mpt 4079  df-id 4309  df-xp 4695  df-rel 4696  df-cnv 4697  df-co 4698  df-dm 4699  df-rn 4700  df-iota 5219  df-fun 5257  df-fn 5258  df-f 5259  df-fo 5261  df-fv 5263  df-2nd 6123
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