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Theorem nfiu1 3997
 Description: Bound-variable hypothesis builder for indexed union. (Contributed by NM, 12-Oct-2003.)
Assertion
Ref Expression
nfiu1 xx A B

Proof of Theorem nfiu1
Dummy variable y is distinct from all other variables.
StepHypRef Expression
1 df-iun 3971 . 2 x A B = {y x A y B}
2 nfre1 2670 . . 3 xx A y B
32nfab 2493 . 2 x{y x A y B}
41, 3nfcxfr 2486 1 xx A B
 Colors of variables: wff setvar class Syntax hints:   ∈ wcel 1710  {cab 2339  Ⅎwnfc 2476  ∃wrex 2615  ∪ciun 3969 This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8  ax-gen 1546  ax-5 1557  ax-17 1616  ax-9 1654  ax-8 1675  ax-6 1729  ax-7 1734  ax-11 1746  ax-12 1925  ax-ext 2334 This theorem depends on definitions:  df-bi 177  df-an 360  df-tru 1319  df-ex 1542  df-nf 1545  df-sb 1649  df-clab 2340  df-cleq 2346  df-clel 2349  df-nfc 2478  df-rex 2620  df-iun 3971 This theorem is referenced by:  ssiun2s  4010  eliunxp  4821  opeliunxp2  4822
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