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Theorem ndmfvg 5525
Description: The value of a class outside its domain is the empty set. (Contributed by Jim Kingdon, 15-Jan-2019.)
Assertion
Ref Expression
ndmfvg ((𝐴 ∈ V ∧ ¬ 𝐴 ∈ dom 𝐹) → (𝐹𝐴) = ∅)

Proof of Theorem ndmfvg
Dummy variable 𝑥 is distinct from all other variables.
StepHypRef Expression
1 euex 2049 . . . . 5 (∃!𝑥 𝐴𝐹𝑥 → ∃𝑥 𝐴𝐹𝑥)
2 eldmg 4804 . . . . 5 (𝐴 ∈ V → (𝐴 ∈ dom 𝐹 ↔ ∃𝑥 𝐴𝐹𝑥))
31, 2syl5ibr 155 . . . 4 (𝐴 ∈ V → (∃!𝑥 𝐴𝐹𝑥𝐴 ∈ dom 𝐹))
43con3d 626 . . 3 (𝐴 ∈ V → (¬ 𝐴 ∈ dom 𝐹 → ¬ ∃!𝑥 𝐴𝐹𝑥))
5 tz6.12-2 5485 . . 3 (¬ ∃!𝑥 𝐴𝐹𝑥 → (𝐹𝐴) = ∅)
64, 5syl6 33 . 2 (𝐴 ∈ V → (¬ 𝐴 ∈ dom 𝐹 → (𝐹𝐴) = ∅))
76imp 123 1 ((𝐴 ∈ V ∧ ¬ 𝐴 ∈ dom 𝐹) → (𝐹𝐴) = ∅)
Colors of variables: wff set class
Syntax hints:  ¬ wn 3  wi 4  wa 103   = wceq 1348  wex 1485  ∃!weu 2019  wcel 2141  Vcvv 2730  c0 3414   class class class wbr 3987  dom cdm 4609  cfv 5196
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-in1 609  ax-in2 610  ax-io 704  ax-5 1440  ax-7 1441  ax-gen 1442  ax-ie1 1486  ax-ie2 1487  ax-8 1497  ax-10 1498  ax-11 1499  ax-i12 1500  ax-bndl 1502  ax-4 1503  ax-17 1519  ax-i9 1523  ax-ial 1527  ax-i5r 1528  ax-ext 2152
This theorem depends on definitions:  df-bi 116  df-3an 975  df-tru 1351  df-fal 1354  df-nf 1454  df-sb 1756  df-eu 2022  df-clab 2157  df-cleq 2163  df-clel 2166  df-nfc 2301  df-ral 2453  df-rex 2454  df-v 2732  df-dif 3123  df-un 3125  df-in 3127  df-ss 3134  df-nul 3415  df-sn 3587  df-pr 3588  df-op 3590  df-uni 3795  df-br 3988  df-dm 4619  df-iota 5158  df-fv 5204
This theorem is referenced by:  ovprc  5885  sumnul  11374
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