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Theorem uniiun 3738
 Description: Class union in terms of indexed union. Definition in [Stoll] p. 43. (Contributed by NM, 28-Jun-1998.)
Assertion
Ref Expression
uniiun 𝐴 = 𝑥𝐴 𝑥
Distinct variable group:   𝑥,𝐴

Proof of Theorem uniiun
Dummy variable 𝑦 is distinct from all other variables.
StepHypRef Expression
1 dfuni2 3610 . 2 𝐴 = {𝑦 ∣ ∃𝑥𝐴 𝑦𝑥}
2 df-iun 3687 . 2 𝑥𝐴 𝑥 = {𝑦 ∣ ∃𝑥𝐴 𝑦𝑥}
31, 2eqtr4i 2079 1 𝐴 = 𝑥𝐴 𝑥
 Colors of variables: wff set class Syntax hints:   = wceq 1259  {cab 2042  ∃wrex 2324  ∪ cuni 3608  ∪ ciun 3685 This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 103  ax-ia2 104  ax-ia3 105  ax-5 1352  ax-7 1353  ax-gen 1354  ax-ie1 1398  ax-ie2 1399  ax-8 1411  ax-11 1413  ax-4 1416  ax-17 1435  ax-i9 1439  ax-ial 1443  ax-i5r 1444  ax-ext 2038 This theorem depends on definitions:  df-bi 114  df-tru 1262  df-nf 1366  df-sb 1662  df-clab 2043  df-cleq 2049  df-rex 2329  df-uni 3609  df-iun 3687 This theorem is referenced by:  iunpwss  3771  truni  3896  iunpw  4239  reluni  4488  rnuni  4763  imauni  5428
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