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Theorem eusv2 4895
 Description: Two ways to express single-valuedness of a class expression 𝐴(𝑥). (Contributed by NM, 15-Oct-2010.) (Proof shortened by Mario Carneiro, 18-Nov-2016.)
Hypothesis
Ref Expression
eusv2.1 𝐴 ∈ V
Assertion
Ref Expression
eusv2 (∃!𝑦𝑥 𝑦 = 𝐴 ↔ ∃!𝑦𝑥 𝑦 = 𝐴)
Distinct variable groups:   𝑥,𝑦   𝑦,𝐴
Allowed substitution hint:   𝐴(𝑥)

Proof of Theorem eusv2
StepHypRef Expression
1 eusv2.1 . . 3 𝐴 ∈ V
21eusv2nf 4894 . 2 (∃!𝑦𝑥 𝑦 = 𝐴𝑥𝐴)
3 eusvnfb 4892 . . 3 (∃!𝑦𝑥 𝑦 = 𝐴 ↔ (𝑥𝐴𝐴 ∈ V))
41, 3mpbiran2 974 . 2 (∃!𝑦𝑥 𝑦 = 𝐴𝑥𝐴)
52, 4bitr4i 267 1 (∃!𝑦𝑥 𝑦 = 𝐴 ↔ ∃!𝑦𝑥 𝑦 = 𝐴)
 Colors of variables: wff setvar class Syntax hints:   ↔ wb 196  ∀wal 1521   = wceq 1523  ∃wex 1744   ∈ wcel 2030  ∃!weu 2498  Ⅎwnfc 2780  Vcvv 3231 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1762  ax-4 1777  ax-5 1879  ax-6 1945  ax-7 1981  ax-9 2039  ax-10 2059  ax-11 2074  ax-12 2087  ax-13 2282  ax-ext 2631 This theorem depends on definitions:  df-bi 197  df-or 384  df-an 385  df-tru 1526  df-fal 1529  df-ex 1745  df-nf 1750  df-sb 1938  df-eu 2502  df-mo 2503  df-clab 2638  df-cleq 2644  df-clel 2647  df-nfc 2782  df-ral 2946  df-rex 2947  df-v 3233  df-sbc 3469  df-csb 3567  df-dif 3610  df-un 3612  df-nul 3949  df-sn 4211  df-pr 4213  df-uni 4469 This theorem is referenced by: (None)
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