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Theorem unipr 4415
Description: The union of a pair is the union of its members. Proposition 5.7 of [TakeutiZaring] p. 16. (Contributed by NM, 23-Aug-1993.)
Hypotheses
Ref Expression
unipr.1 𝐴 ∈ V
unipr.2 𝐵 ∈ V
Assertion
Ref Expression
unipr {𝐴, 𝐵} = (𝐴𝐵)

Proof of Theorem unipr
Dummy variables 𝑥 𝑦 are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 19.43 1807 . . . 4 (∃𝑦((𝑥𝑦𝑦 = 𝐴) ∨ (𝑥𝑦𝑦 = 𝐵)) ↔ (∃𝑦(𝑥𝑦𝑦 = 𝐴) ∨ ∃𝑦(𝑥𝑦𝑦 = 𝐵)))
2 vex 3189 . . . . . . . 8 𝑦 ∈ V
32elpr 4169 . . . . . . 7 (𝑦 ∈ {𝐴, 𝐵} ↔ (𝑦 = 𝐴𝑦 = 𝐵))
43anbi2i 729 . . . . . 6 ((𝑥𝑦𝑦 ∈ {𝐴, 𝐵}) ↔ (𝑥𝑦 ∧ (𝑦 = 𝐴𝑦 = 𝐵)))
5 andi 910 . . . . . 6 ((𝑥𝑦 ∧ (𝑦 = 𝐴𝑦 = 𝐵)) ↔ ((𝑥𝑦𝑦 = 𝐴) ∨ (𝑥𝑦𝑦 = 𝐵)))
64, 5bitri 264 . . . . 5 ((𝑥𝑦𝑦 ∈ {𝐴, 𝐵}) ↔ ((𝑥𝑦𝑦 = 𝐴) ∨ (𝑥𝑦𝑦 = 𝐵)))
76exbii 1771 . . . 4 (∃𝑦(𝑥𝑦𝑦 ∈ {𝐴, 𝐵}) ↔ ∃𝑦((𝑥𝑦𝑦 = 𝐴) ∨ (𝑥𝑦𝑦 = 𝐵)))
8 unipr.1 . . . . . . 7 𝐴 ∈ V
98clel3 3324 . . . . . 6 (𝑥𝐴 ↔ ∃𝑦(𝑦 = 𝐴𝑥𝑦))
10 exancom 1784 . . . . . 6 (∃𝑦(𝑦 = 𝐴𝑥𝑦) ↔ ∃𝑦(𝑥𝑦𝑦 = 𝐴))
119, 10bitri 264 . . . . 5 (𝑥𝐴 ↔ ∃𝑦(𝑥𝑦𝑦 = 𝐴))
12 unipr.2 . . . . . . 7 𝐵 ∈ V
1312clel3 3324 . . . . . 6 (𝑥𝐵 ↔ ∃𝑦(𝑦 = 𝐵𝑥𝑦))
14 exancom 1784 . . . . . 6 (∃𝑦(𝑦 = 𝐵𝑥𝑦) ↔ ∃𝑦(𝑥𝑦𝑦 = 𝐵))
1513, 14bitri 264 . . . . 5 (𝑥𝐵 ↔ ∃𝑦(𝑥𝑦𝑦 = 𝐵))
1611, 15orbi12i 543 . . . 4 ((𝑥𝐴𝑥𝐵) ↔ (∃𝑦(𝑥𝑦𝑦 = 𝐴) ∨ ∃𝑦(𝑥𝑦𝑦 = 𝐵)))
171, 7, 163bitr4ri 293 . . 3 ((𝑥𝐴𝑥𝐵) ↔ ∃𝑦(𝑥𝑦𝑦 ∈ {𝐴, 𝐵}))
1817abbii 2736 . 2 {𝑥 ∣ (𝑥𝐴𝑥𝐵)} = {𝑥 ∣ ∃𝑦(𝑥𝑦𝑦 ∈ {𝐴, 𝐵})}
19 df-un 3560 . 2 (𝐴𝐵) = {𝑥 ∣ (𝑥𝐴𝑥𝐵)}
20 df-uni 4403 . 2 {𝐴, 𝐵} = {𝑥 ∣ ∃𝑦(𝑥𝑦𝑦 ∈ {𝐴, 𝐵})}
2118, 19, 203eqtr4ri 2654 1 {𝐴, 𝐵} = (𝐴𝐵)
Colors of variables: wff setvar class
Syntax hints:  wo 383  wa 384   = wceq 1480  wex 1701  wcel 1987  {cab 2607  Vcvv 3186  cun 3553  {cpr 4150   cuni 4402
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1719  ax-4 1734  ax-5 1836  ax-6 1885  ax-7 1932  ax-9 1996  ax-10 2016  ax-11 2031  ax-12 2044  ax-13 2245  ax-ext 2601
This theorem depends on definitions:  df-bi 197  df-or 385  df-an 386  df-tru 1483  df-ex 1702  df-nf 1707  df-sb 1878  df-clab 2608  df-cleq 2614  df-clel 2617  df-nfc 2750  df-v 3188  df-un 3560  df-sn 4149  df-pr 4151  df-uni 4403
This theorem is referenced by:  uniprg  4416  unisn  4417  uniintsn  4479  uniop  4937  unex  6909  rankxplim  8686  mrcun  16203  indistps  20725  indistps2  20726  leordtval2  20926  ex-uni  27137  fouriersw  39752
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