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Theorem dfuni2 3573
Description: Alternate definition of class union. (Contributed by NM, 28-Jun-1998.)
Assertion
Ref Expression
dfuni2  U.  {  |  }
Distinct variable group:   ,,

Proof of Theorem dfuni2
StepHypRef Expression
1 df-uni 3572 . 2  U.  {  |  }
2 exancom 1496 . . . 4
3 df-rex 2306 . . . 4
42, 3bitr4i 176 . . 3
54abbii 2150 . 2  {  |  }  {  |  }
61, 5eqtri 2057 1  U.  {  |  }
Colors of variables: wff set class
Syntax hints:   wa 97   wceq 1242  wex 1378   wcel 1390   {cab 2023  wrex 2301   U.cuni 3571
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 99  ax-ia2 100  ax-ia3 101  ax-5 1333  ax-7 1334  ax-gen 1335  ax-ie1 1379  ax-ie2 1380  ax-8 1392  ax-11 1394  ax-4 1397  ax-17 1416  ax-i9 1420  ax-ial 1424  ax-i5r 1425  ax-ext 2019
This theorem depends on definitions:  df-bi 110  df-tru 1245  df-nf 1347  df-sb 1643  df-clab 2024  df-cleq 2030  df-rex 2306  df-uni 3572
This theorem is referenced by:  nfuni  3577  nfunid  3578  unieq  3580  uniiun  3701
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