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Theorem iotaexOLD 6522
Description: Obsolete version of iotaex 6515 as of 23-Dec-2024. (Contributed by Andrew Salmon, 11-Jul-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
Assertion
Ref Expression
iotaexOLD (℩𝑥𝜑) ∈ V

Proof of Theorem iotaexOLD
Dummy variable 𝑧 is distinct from all other variables.
StepHypRef Expression
1 iotaval 6513 . . . . 5 (∀𝑥(𝜑𝑥 = 𝑧) → (℩𝑥𝜑) = 𝑧)
21eqcomd 2736 . . . 4 (∀𝑥(𝜑𝑥 = 𝑧) → 𝑧 = (℩𝑥𝜑))
32eximi 1835 . . 3 (∃𝑧𝑥(𝜑𝑥 = 𝑧) → ∃𝑧 𝑧 = (℩𝑥𝜑))
4 eu6 2566 . . 3 (∃!𝑥𝜑 ↔ ∃𝑧𝑥(𝜑𝑥 = 𝑧))
5 isset 3485 . . 3 ((℩𝑥𝜑) ∈ V ↔ ∃𝑧 𝑧 = (℩𝑥𝜑))
63, 4, 53imtr4i 291 . 2 (∃!𝑥𝜑 → (℩𝑥𝜑) ∈ V)
7 iotanul 6520 . . 3 (¬ ∃!𝑥𝜑 → (℩𝑥𝜑) = ∅)
8 0ex 5306 . . 3 ∅ ∈ V
97, 8eqeltrdi 2839 . 2 (¬ ∃!𝑥𝜑 → (℩𝑥𝜑) ∈ V)
106, 9pm2.61i 182 1 (℩𝑥𝜑) ∈ V
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wb 205  wal 1537   = wceq 1539  wex 1779  wcel 2104  ∃!weu 2560  Vcvv 3472  c0 4321  cio 6492
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1795  ax-4 1809  ax-5 1911  ax-6 1969  ax-7 2009  ax-8 2106  ax-9 2114  ax-10 2135  ax-11 2152  ax-12 2169  ax-ext 2701  ax-nul 5305
This theorem depends on definitions:  df-bi 206  df-an 395  df-or 844  df-tru 1542  df-fal 1552  df-ex 1780  df-nf 1784  df-sb 2066  df-mo 2532  df-eu 2561  df-clab 2708  df-cleq 2722  df-clel 2808  df-ral 3060  df-rex 3069  df-v 3474  df-dif 3950  df-un 3952  df-in 3954  df-ss 3964  df-nul 4322  df-sn 4628  df-pr 4630  df-uni 4908  df-iota 6494
This theorem is referenced by: (None)
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