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Theorem nfcvf 2244
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 2223 . 2  |-  F/_ x
z
2 nfcv 2223 . 2  |-  F/_ z
y
3 id 19 . 2  |-  ( z  =  y  ->  z  =  y )
41, 2, 3dvelimc 2243 1  |-  ( -. 
A. x  x  =  y  ->  F/_ x y )
Colors of variables: wff set class
Syntax hints:   -. wn 3    -> wi 4   A.wal 1283   F/_wnfc 2210
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 104  ax-ia2 105  ax-ia3 106  ax-in1 577  ax-in2 578  ax-io 663  ax-5 1377  ax-7 1378  ax-gen 1379  ax-ie1 1423  ax-ie2 1424  ax-8 1436  ax-10 1437  ax-11 1438  ax-i12 1439  ax-bndl 1440  ax-4 1441  ax-17 1460  ax-i9 1464  ax-ial 1468  ax-i5r 1469  ax-ext 2065
This theorem depends on definitions:  df-bi 115  df-tru 1288  df-fal 1291  df-nf 1391  df-sb 1688  df-cleq 2076  df-clel 2079  df-nfc 2212
This theorem is referenced by:  nfcvf2  2245
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