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Theorem iuncom 4917
Description: Commutation of indexed unions. (Contributed by NM, 18-Dec-2008.)
Assertion
Ref Expression
iuncom 𝑥𝐴 𝑦𝐵 𝐶 = 𝑦𝐵 𝑥𝐴 𝐶
Distinct variable groups:   𝑦,𝐴   𝑥,𝐵   𝑥,𝑦
Allowed substitution hints:   𝐴(𝑥)   𝐵(𝑦)   𝐶(𝑥,𝑦)

Proof of Theorem iuncom
Dummy variable 𝑧 is distinct from all other variables.
StepHypRef Expression
1 rexcom 3352 . . . 4 (∃𝑥𝐴𝑦𝐵 𝑧𝐶 ↔ ∃𝑦𝐵𝑥𝐴 𝑧𝐶)
2 eliun 4914 . . . . 5 (𝑧 𝑦𝐵 𝐶 ↔ ∃𝑦𝐵 𝑧𝐶)
32rexbii 3244 . . . 4 (∃𝑥𝐴 𝑧 𝑦𝐵 𝐶 ↔ ∃𝑥𝐴𝑦𝐵 𝑧𝐶)
4 eliun 4914 . . . . 5 (𝑧 𝑥𝐴 𝐶 ↔ ∃𝑥𝐴 𝑧𝐶)
54rexbii 3244 . . . 4 (∃𝑦𝐵 𝑧 𝑥𝐴 𝐶 ↔ ∃𝑦𝐵𝑥𝐴 𝑧𝐶)
61, 3, 53bitr4i 304 . . 3 (∃𝑥𝐴 𝑧 𝑦𝐵 𝐶 ↔ ∃𝑦𝐵 𝑧 𝑥𝐴 𝐶)
7 eliun 4914 . . 3 (𝑧 𝑥𝐴 𝑦𝐵 𝐶 ↔ ∃𝑥𝐴 𝑧 𝑦𝐵 𝐶)
8 eliun 4914 . . 3 (𝑧 𝑦𝐵 𝑥𝐴 𝐶 ↔ ∃𝑦𝐵 𝑧 𝑥𝐴 𝐶)
96, 7, 83bitr4i 304 . 2 (𝑧 𝑥𝐴 𝑦𝐵 𝐶𝑧 𝑦𝐵 𝑥𝐴 𝐶)
109eqriv 2815 1 𝑥𝐴 𝑦𝐵 𝐶 = 𝑦𝐵 𝑥𝐴 𝐶
Colors of variables: wff setvar class
Syntax hints:   = wceq 1528  wcel 2105  wrex 3136   ciun 4910
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1787  ax-4 1801  ax-5 1902  ax-6 1961  ax-7 2006  ax-8 2107  ax-9 2115  ax-10 2136  ax-11 2151  ax-12 2167  ax-ext 2790
This theorem depends on definitions:  df-bi 208  df-an 397  df-or 842  df-tru 1531  df-ex 1772  df-nf 1776  df-sb 2061  df-clab 2797  df-cleq 2811  df-clel 2890  df-nfc 2960  df-ral 3140  df-rex 3141  df-v 3494  df-iun 4912
This theorem is referenced by: (None)
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