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Theorem wfrlem2 25471
Description: Lemma for well-founded recursion. An acceptable function is a function. (Contributed by Scott Fenton, 21-Apr-2011.)
Hypothesis
Ref Expression
wfrlem1.1  |-  B  =  { f  |  E. x ( f  Fn  x  /\  ( x 
C_  A  /\  A. y  e.  x  Pred ( R ,  A , 
y )  C_  x
)  /\  A. y  e.  x  ( f `  y )  =  ( G `  ( f  |`  Pred ( R ,  A ,  y )
) ) ) }
Assertion
Ref Expression
wfrlem2  |-  ( g  e.  B  ->  Fun  g )
Distinct variable groups:    A, f,
g, x, y    f, G, g, x, y    R, f, g, x, y
Allowed substitution hints:    B( x, y, f, g)

Proof of Theorem wfrlem2
Dummy variables  w  z are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 wfrlem1.1 . . . 4  |-  B  =  { f  |  E. x ( f  Fn  x  /\  ( x 
C_  A  /\  A. y  e.  x  Pred ( R ,  A , 
y )  C_  x
)  /\  A. y  e.  x  ( f `  y )  =  ( G `  ( f  |`  Pred ( R ,  A ,  y )
) ) ) }
21wfrlem1 25470 . . 3  |-  B  =  { g  |  E. z ( g  Fn  z  /\  ( z 
C_  A  /\  A. w  e.  z  Pred ( R ,  A ,  w )  C_  z
)  /\  A. w  e.  z  ( g `  w )  =  ( G `  ( g  |`  Pred ( R ,  A ,  w )
) ) ) }
32abeq2i 2511 . 2  |-  ( g  e.  B  <->  E. z
( g  Fn  z  /\  ( z  C_  A  /\  A. w  e.  z 
Pred ( R ,  A ,  w )  C_  z )  /\  A. w  e.  z  (
g `  w )  =  ( G `  ( g  |`  Pred ( R ,  A ,  w ) ) ) ) )
4 fnfun 5501 . . . 4  |-  ( g  Fn  z  ->  Fun  g )
543ad2ant1 978 . . 3  |-  ( ( g  Fn  z  /\  ( z  C_  A  /\  A. w  e.  z 
Pred ( R ,  A ,  w )  C_  z )  /\  A. w  e.  z  (
g `  w )  =  ( G `  ( g  |`  Pred ( R ,  A ,  w ) ) ) )  ->  Fun  g )
65exlimiv 1641 . 2  |-  ( E. z ( g  Fn  z  /\  ( z 
C_  A  /\  A. w  e.  z  Pred ( R ,  A ,  w )  C_  z
)  /\  A. w  e.  z  ( g `  w )  =  ( G `  ( g  |`  Pred ( R ,  A ,  w )
) ) )  ->  Fun  g )
73, 6sylbi 188 1  |-  ( g  e.  B  ->  Fun  g )
Colors of variables: wff set class
Syntax hints:    -> wi 4    /\ wa 359    /\ w3a 936   E.wex 1547    = wceq 1649    e. wcel 1721   {cab 2390   A.wral 2666    C_ wss 3280    |` cres 4839   Fun wfun 5407    Fn wfn 5408   ` cfv 5413   Predcpred 25381
This theorem is referenced by:  wfrlem4  25473  wfrlem5  25474  wfrlem6  25475
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8  ax-gen 1552  ax-5 1563  ax-17 1623  ax-9 1662  ax-8 1683  ax-6 1740  ax-7 1745  ax-11 1757  ax-12 1946  ax-ext 2385
This theorem depends on definitions:  df-bi 178  df-or 360  df-an 361  df-3an 938  df-tru 1325  df-ex 1548  df-nf 1551  df-sb 1656  df-clab 2391  df-cleq 2397  df-clel 2400  df-nfc 2529  df-ral 2671  df-rex 2672  df-rab 2675  df-v 2918  df-dif 3283  df-un 3285  df-in 3287  df-ss 3294  df-nul 3589  df-if 3700  df-sn 3780  df-pr 3781  df-op 3783  df-uni 3976  df-br 4173  df-opab 4227  df-xp 4843  df-rel 4844  df-cnv 4845  df-co 4846  df-dm 4847  df-rn 4848  df-res 4849  df-ima 4850  df-iota 5377  df-fun 5415  df-fn 5416  df-fv 5421  df-pred 25382
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