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Theorem nfiu1 3811
Description: Bound-variable hypothesis builder for indexed union. (Contributed by NM, 12-Oct-2003.)
Assertion
Ref Expression
nfiu1 𝑥 𝑥𝐴 𝐵

Proof of Theorem nfiu1
Dummy variable 𝑦 is distinct from all other variables.
StepHypRef Expression
1 df-iun 3783 . 2 𝑥𝐴 𝐵 = {𝑦 ∣ ∃𝑥𝐴 𝑦𝐵}
2 nfre1 2451 . . 3 𝑥𝑥𝐴 𝑦𝐵
32nfab 2261 . 2 𝑥{𝑦 ∣ ∃𝑥𝐴 𝑦𝐵}
41, 3nfcxfr 2253 1 𝑥 𝑥𝐴 𝐵
Colors of variables: wff set class
Syntax hints:  wcel 1463  {cab 2101  wnfc 2243  wrex 2392   ciun 3781
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-io 681  ax-5 1406  ax-7 1407  ax-gen 1408  ax-ie1 1452  ax-ie2 1453  ax-8 1465  ax-10 1466  ax-11 1467  ax-i12 1468  ax-bndl 1469  ax-4 1470  ax-17 1489  ax-i9 1493  ax-ial 1497  ax-i5r 1498  ax-ext 2097
This theorem depends on definitions:  df-bi 116  df-nf 1420  df-sb 1719  df-clab 2102  df-cleq 2108  df-clel 2111  df-nfc 2245  df-rex 2397  df-iun 3783
This theorem is referenced by:  ssiun2s  3825  triun  4007  eliunxp  4646  opeliunxp2  4647  opeliunxp2f  6101  ixpf  6580  ctiunctlemfo  11858
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