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Theorem unisn3 4646
 Description: Union of a singleton in the form of a restricted class abstraction. (Contributed by NM, 3-Jul-2008.)
Assertion
Ref Expression
unisn3 (𝐴𝐵 {𝑥𝐵𝑥 = 𝐴} = 𝐴)
Distinct variable groups:   𝑥,𝐴   𝑥,𝐵

Proof of Theorem unisn3
StepHypRef Expression
1 rabsn 4444 . . 3 (𝐴𝐵 → {𝑥𝐵𝑥 = 𝐴} = {𝐴})
21unieqd 4637 . 2 (𝐴𝐵 {𝑥𝐵𝑥 = 𝐴} = {𝐴})
3 unisng 4642 . 2 (𝐴𝐵 {𝐴} = 𝐴)
42, 3eqtrd 2832 1 (𝐴𝐵 {𝑥𝐵𝑥 = 𝐴} = 𝐴)
 Colors of variables: wff setvar class Syntax hints:   → wi 4   = wceq 1653   ∈ wcel 2157  {crab 3092  {csn 4367  ∪ cuni 4627 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1891  ax-4 1905  ax-5 2006  ax-6 2072  ax-7 2107  ax-9 2166  ax-10 2185  ax-11 2200  ax-12 2213  ax-ext 2776 This theorem depends on definitions:  df-bi 199  df-an 386  df-or 875  df-tru 1657  df-ex 1876  df-nf 1880  df-sb 2065  df-clab 2785  df-cleq 2791  df-clel 2794  df-nfc 2929  df-rex 3094  df-rab 3097  df-v 3386  df-un 3773  df-sn 4368  df-pr 4370  df-uni 4628 This theorem is referenced by: (None)
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