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Theorem csbifg 3593
Description: Distribute proper substitution through the conditional operator. (Contributed by NM, 24-Feb-2013.) (Revised by Mario Carneiro, 14-Nov-2016.)
Assertion
Ref Expression
csbifg  |-  ( A  e.  V  ->  [_ A  /  x ]_ if (
ph ,  B ,  C )  =  if ( [. A  /  x ]. ph ,  [_ A  /  x ]_ B ,  [_ A  /  x ]_ C ) )

Proof of Theorem csbifg
Dummy variable  y is distinct from all other variables.
StepHypRef Expression
1 csbeq1 3084 . . 3  |-  ( y  =  A  ->  [_ y  /  x ]_ if (
ph ,  B ,  C )  =  [_ A  /  x ]_ if ( ph ,  B ,  C ) )
2 dfsbcq2 2994 . . . 4  |-  ( y  =  A  ->  ( [ y  /  x ] ph  <->  [. A  /  x ]. ph ) )
3 csbeq1 3084 . . . 4  |-  ( y  =  A  ->  [_ y  /  x ]_ B  = 
[_ A  /  x ]_ B )
4 csbeq1 3084 . . . 4  |-  ( y  =  A  ->  [_ y  /  x ]_ C  = 
[_ A  /  x ]_ C )
52, 3, 4ifbieq12d 3587 . . 3  |-  ( y  =  A  ->  if ( [ y  /  x ] ph ,  [_ y  /  x ]_ B ,  [_ y  /  x ]_ C )  =  if ( [. A  /  x ]. ph ,  [_ A  /  x ]_ B ,  [_ A  /  x ]_ C ) )
61, 5eqeq12d 2297 . 2  |-  ( y  =  A  ->  ( [_ y  /  x ]_ if ( ph ,  B ,  C )  =  if ( [ y  /  x ] ph ,  [_ y  /  x ]_ B ,  [_ y  /  x ]_ C )  <->  [_ A  /  x ]_ if ( ph ,  B ,  C )  =  if ( [. A  /  x ]. ph ,  [_ A  /  x ]_ B ,  [_ A  /  x ]_ C ) ) )
7 vex 2791 . . 3  |-  y  e. 
_V
8 nfs1v 2045 . . . 4  |-  F/ x [ y  /  x ] ph
9 nfcsb1v 3113 . . . 4  |-  F/_ x [_ y  /  x ]_ B
10 nfcsb1v 3113 . . . 4  |-  F/_ x [_ y  /  x ]_ C
118, 9, 10nfif 3589 . . 3  |-  F/_ x if ( [ y  /  x ] ph ,  [_ y  /  x ]_ B ,  [_ y  /  x ]_ C )
12 sbequ12 1860 . . . 4  |-  ( x  =  y  ->  ( ph 
<->  [ y  /  x ] ph ) )
13 csbeq1a 3089 . . . 4  |-  ( x  =  y  ->  B  =  [_ y  /  x ]_ B )
14 csbeq1a 3089 . . . 4  |-  ( x  =  y  ->  C  =  [_ y  /  x ]_ C )
1512, 13, 14ifbieq12d 3587 . . 3  |-  ( x  =  y  ->  if ( ph ,  B ,  C )  =  if ( [ y  /  x ] ph ,  [_ y  /  x ]_ B ,  [_ y  /  x ]_ C ) )
167, 11, 15csbief 3122 . 2  |-  [_ y  /  x ]_ if (
ph ,  B ,  C )  =  if ( [ y  /  x ] ph ,  [_ y  /  x ]_ B ,  [_ y  /  x ]_ C )
176, 16vtoclg 2843 1  |-  ( A  e.  V  ->  [_ A  /  x ]_ if (
ph ,  B ,  C )  =  if ( [. A  /  x ]. ph ,  [_ A  /  x ]_ B ,  [_ A  /  x ]_ C ) )
Colors of variables: wff set class
Syntax hints:    -> wi 4    = wceq 1623   [wsb 1629    e. wcel 1684   [.wsbc 2991   [_csb 3081   ifcif 3565
This theorem is referenced by:  cdlemk40  31106
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-6 1703  ax-7 1708  ax-11 1715  ax-12 1866  ax-ext 2264
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-clab 2270  df-cleq 2276  df-clel 2279  df-nfc 2408  df-rab 2552  df-v 2790  df-sbc 2992  df-csb 3082  df-un 3157  df-if 3566
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