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Theorem reu0 4259
 Description: Vacuous restricted uniqueness is always false. (Contributed by AV, 3-Apr-2023.)
Assertion
Ref Expression
reu0 ¬ ∃!𝑥 ∈ ∅ 𝜑

Proof of Theorem reu0
StepHypRef Expression
1 rex0 4258 . 2 ¬ ∃𝑥 ∈ ∅ 𝜑
2 reurex 3341 . 2 (∃!𝑥 ∈ ∅ 𝜑 → ∃𝑥 ∈ ∅ 𝜑)
31, 2mto 200 1 ¬ ∃!𝑥 ∈ ∅ 𝜑
 Colors of variables: wff setvar class Syntax hints:  ¬ wn 3  ∃wrex 3071  ∃!wreu 3072  ∅c0 4227 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1797  ax-4 1811  ax-5 1911  ax-6 1970  ax-7 2015  ax-8 2113  ax-9 2121  ax-ext 2729 This theorem depends on definitions:  df-bi 210  df-an 400  df-ex 1782  df-sb 2070  df-eu 2588  df-clab 2736  df-cleq 2750  df-clel 2830  df-ral 3075  df-rex 3076  df-reu 3077  df-rmo 3078  df-dif 3863  df-nul 4228 This theorem is referenced by:  meet0  17826  join0  17827
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