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Theorem nfimd 1578
Description: If in a context  x is not free in  ps and  ch, then it is not free in  ( ps  ->  ch ). (Contributed by Mario Carneiro, 24-Sep-2016.) (Proof shortened by Wolf Lammen, 30-Dec-2017.)
Hypotheses
Ref Expression
nfimd.1  |-  ( ph  ->  F/ x ps )
nfimd.2  |-  ( ph  ->  F/ x ch )
Assertion
Ref Expression
nfimd  |-  ( ph  ->  F/ x ( ps 
->  ch ) )

Proof of Theorem nfimd
StepHypRef Expression
1 nfimd.1 . 2  |-  ( ph  ->  F/ x ps )
2 nfimd.2 . 2  |-  ( ph  ->  F/ x ch )
3 nfnf1 1537 . . . . 5  |-  F/ x F/ x ps
43nfri 1512 . . . 4  |-  ( F/ x ps  ->  A. x F/ x ps )
5 nfnf1 1537 . . . . 5  |-  F/ x F/ x ch
65nfri 1512 . . . 4  |-  ( F/ x ch  ->  A. x F/ x ch )
7 nfr 1511 . . . . . 6  |-  ( F/ x ch  ->  ( ch  ->  A. x ch )
)
87imim2d 54 . . . . 5  |-  ( F/ x ch  ->  (
( ps  ->  ch )  ->  ( ps  ->  A. x ch ) ) )
9 19.21t 1575 . . . . . 6  |-  ( F/ x ps  ->  ( A. x ( ps  ->  ch )  <->  ( ps  ->  A. x ch ) ) )
109biimprd 157 . . . . 5  |-  ( F/ x ps  ->  (
( ps  ->  A. x ch )  ->  A. x
( ps  ->  ch ) ) )
118, 10syl9r 73 . . . 4  |-  ( F/ x ps  ->  ( F/ x ch  ->  (
( ps  ->  ch )  ->  A. x ( ps 
->  ch ) ) ) )
124, 6, 11alrimdh 1472 . . 3  |-  ( F/ x ps  ->  ( F/ x ch  ->  A. x
( ( ps  ->  ch )  ->  A. x
( ps  ->  ch ) ) ) )
13 df-nf 1454 . . 3  |-  ( F/ x ( ps  ->  ch )  <->  A. x ( ( ps  ->  ch )  ->  A. x ( ps 
->  ch ) ) )
1412, 13syl6ibr 161 . 2  |-  ( F/ x ps  ->  ( F/ x ch  ->  F/ x ( ps  ->  ch ) ) )
151, 2, 14sylc 62 1  |-  ( ph  ->  F/ x ( ps 
->  ch ) )
Colors of variables: wff set class
Syntax hints:    -> wi 4   A.wal 1346   F/wnf 1453
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-5 1440  ax-gen 1442  ax-4 1503  ax-ial 1527  ax-i5r 1528
This theorem depends on definitions:  df-bi 116  df-nf 1454
This theorem is referenced by:  nfbid  1581  dvelimALT  2003  dvelimfv  2004  dvelimor  2011  nfmod  2036  nfraldw  2502  nfraldxy  2503  nfixpxy  6693  cbvrald  13788
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