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Theorem nfcvf 2304
Description: If  x and  y are distinct, then  x is not free in  y. (Contributed by Mario Carneiro, 8-Oct-2016.)
Assertion
Ref Expression
nfcvf  |-  ( -. 
A. x  x  =  y  ->  F/_ x y )

Proof of Theorem nfcvf
Dummy variable  z is distinct from all other variables.
StepHypRef Expression
1 nfcv 2282 . 2  |-  F/_ x
z
2 nfcv 2282 . 2  |-  F/_ z
y
3 id 19 . 2  |-  ( z  =  y  ->  z  =  y )
41, 2, 3dvelimc 2303 1  |-  ( -. 
A. x  x  =  y  ->  F/_ x y )
Colors of variables: wff set class
Syntax hints:   -. wn 3    -> wi 4   A.wal 1330   F/_wnfc 2269
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-in1 604  ax-in2 605  ax-io 699  ax-5 1424  ax-7 1425  ax-gen 1426  ax-ie1 1470  ax-ie2 1471  ax-8 1483  ax-10 1484  ax-11 1485  ax-i12 1486  ax-bndl 1487  ax-4 1488  ax-17 1507  ax-i9 1511  ax-ial 1515  ax-i5r 1516  ax-ext 2122
This theorem depends on definitions:  df-bi 116  df-tru 1335  df-fal 1338  df-nf 1438  df-sb 1737  df-cleq 2133  df-clel 2136  df-nfc 2271
This theorem is referenced by:  nfcvf2  2305
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