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Theorem reusv2 4872
 Description: Two ways to express single-valuedness of a class expression 𝐶(𝑦) that is constant for those 𝑦 ∈ 𝐵 such that 𝜑. The first antecedent ensures that the constant value belongs to the existential uniqueness domain 𝐴, and the second ensures that 𝐶(𝑦) is evaluated for at least one 𝑦. (Contributed by NM, 4-Jan-2013.) (Proof shortened by Mario Carneiro, 19-Nov-2016.)
Assertion
Ref Expression
reusv2 ((∀𝑦𝐵 (𝜑𝐶𝐴) ∧ ∃𝑦𝐵 𝜑) → (∃!𝑥𝐴𝑦𝐵 (𝜑𝑥 = 𝐶) ↔ ∃!𝑥𝐴𝑦𝐵 (𝜑𝑥 = 𝐶)))
Distinct variable groups:   𝑥,𝑦,𝐴   𝑥,𝐵   𝑥,𝐶   𝜑,𝑥
Allowed substitution hints:   𝜑(𝑦)   𝐵(𝑦)   𝐶(𝑦)

Proof of Theorem reusv2
Dummy variable 𝑧 is distinct from all other variables.
StepHypRef Expression
1 nfrab1 3120 . . . 4 𝑦{𝑦𝐵𝜑}
2 nfcv 2763 . . . 4 𝑧{𝑦𝐵𝜑}
3 nfv 1842 . . . 4 𝑧 𝐶𝐴
4 nfcsb1v 3547 . . . . 5 𝑦𝑧 / 𝑦𝐶
54nfel1 2778 . . . 4 𝑦𝑧 / 𝑦𝐶𝐴
6 csbeq1a 3540 . . . . 5 (𝑦 = 𝑧𝐶 = 𝑧 / 𝑦𝐶)
76eleq1d 2685 . . . 4 (𝑦 = 𝑧 → (𝐶𝐴𝑧 / 𝑦𝐶𝐴))
81, 2, 3, 5, 7cbvralf 3163 . . 3 (∀𝑦 ∈ {𝑦𝐵𝜑}𝐶𝐴 ↔ ∀𝑧 ∈ {𝑦𝐵𝜑}𝑧 / 𝑦𝐶𝐴)
9 rabid 3114 . . . . . 6 (𝑦 ∈ {𝑦𝐵𝜑} ↔ (𝑦𝐵𝜑))
109imbi1i 339 . . . . 5 ((𝑦 ∈ {𝑦𝐵𝜑} → 𝐶𝐴) ↔ ((𝑦𝐵𝜑) → 𝐶𝐴))
11 impexp 462 . . . . 5 (((𝑦𝐵𝜑) → 𝐶𝐴) ↔ (𝑦𝐵 → (𝜑𝐶𝐴)))
1210, 11bitri 264 . . . 4 ((𝑦 ∈ {𝑦𝐵𝜑} → 𝐶𝐴) ↔ (𝑦𝐵 → (𝜑𝐶𝐴)))
1312ralbii2 2977 . . 3 (∀𝑦 ∈ {𝑦𝐵𝜑}𝐶𝐴 ↔ ∀𝑦𝐵 (𝜑𝐶𝐴))
148, 13bitr3i 266 . 2 (∀𝑧 ∈ {𝑦𝐵𝜑}𝑧 / 𝑦𝐶𝐴 ↔ ∀𝑦𝐵 (𝜑𝐶𝐴))
15 rabn0 3956 . 2 ({𝑦𝐵𝜑} ≠ ∅ ↔ ∃𝑦𝐵 𝜑)
16 reusv2lem5 4871 . . 3 ((∀𝑧 ∈ {𝑦𝐵𝜑}𝑧 / 𝑦𝐶𝐴 ∧ {𝑦𝐵𝜑} ≠ ∅) → (∃!𝑥𝐴𝑧 ∈ {𝑦𝐵𝜑}𝑥 = 𝑧 / 𝑦𝐶 ↔ ∃!𝑥𝐴𝑧 ∈ {𝑦𝐵𝜑}𝑥 = 𝑧 / 𝑦𝐶))
17 nfv 1842 . . . . . 6 𝑧 𝑥 = 𝐶
184nfeq2 2779 . . . . . 6 𝑦 𝑥 = 𝑧 / 𝑦𝐶
196eqeq2d 2631 . . . . . 6 (𝑦 = 𝑧 → (𝑥 = 𝐶𝑥 = 𝑧 / 𝑦𝐶))
201, 2, 17, 18, 19cbvrexf 3164 . . . . 5 (∃𝑦 ∈ {𝑦𝐵𝜑}𝑥 = 𝐶 ↔ ∃𝑧 ∈ {𝑦𝐵𝜑}𝑥 = 𝑧 / 𝑦𝐶)
219anbi1i 731 . . . . . . 7 ((𝑦 ∈ {𝑦𝐵𝜑} ∧ 𝑥 = 𝐶) ↔ ((𝑦𝐵𝜑) ∧ 𝑥 = 𝐶))
22 anass 681 . . . . . . 7 (((𝑦𝐵𝜑) ∧ 𝑥 = 𝐶) ↔ (𝑦𝐵 ∧ (𝜑𝑥 = 𝐶)))
2321, 22bitri 264 . . . . . 6 ((𝑦 ∈ {𝑦𝐵𝜑} ∧ 𝑥 = 𝐶) ↔ (𝑦𝐵 ∧ (𝜑𝑥 = 𝐶)))
2423rexbii2 3037 . . . . 5 (∃𝑦 ∈ {𝑦𝐵𝜑}𝑥 = 𝐶 ↔ ∃𝑦𝐵 (𝜑𝑥 = 𝐶))
2520, 24bitr3i 266 . . . 4 (∃𝑧 ∈ {𝑦𝐵𝜑}𝑥 = 𝑧 / 𝑦𝐶 ↔ ∃𝑦𝐵 (𝜑𝑥 = 𝐶))
2625reubii 3126 . . 3 (∃!𝑥𝐴𝑧 ∈ {𝑦𝐵𝜑}𝑥 = 𝑧 / 𝑦𝐶 ↔ ∃!𝑥𝐴𝑦𝐵 (𝜑𝑥 = 𝐶))
271, 2, 17, 18, 19cbvralf 3163 . . . . 5 (∀𝑦 ∈ {𝑦𝐵𝜑}𝑥 = 𝐶 ↔ ∀𝑧 ∈ {𝑦𝐵𝜑}𝑥 = 𝑧 / 𝑦𝐶)
289imbi1i 339 . . . . . . 7 ((𝑦 ∈ {𝑦𝐵𝜑} → 𝑥 = 𝐶) ↔ ((𝑦𝐵𝜑) → 𝑥 = 𝐶))
29 impexp 462 . . . . . . 7 (((𝑦𝐵𝜑) → 𝑥 = 𝐶) ↔ (𝑦𝐵 → (𝜑𝑥 = 𝐶)))
3028, 29bitri 264 . . . . . 6 ((𝑦 ∈ {𝑦𝐵𝜑} → 𝑥 = 𝐶) ↔ (𝑦𝐵 → (𝜑𝑥 = 𝐶)))
3130ralbii2 2977 . . . . 5 (∀𝑦 ∈ {𝑦𝐵𝜑}𝑥 = 𝐶 ↔ ∀𝑦𝐵 (𝜑𝑥 = 𝐶))
3227, 31bitr3i 266 . . . 4 (∀𝑧 ∈ {𝑦𝐵𝜑}𝑥 = 𝑧 / 𝑦𝐶 ↔ ∀𝑦𝐵 (𝜑𝑥 = 𝐶))
3332reubii 3126 . . 3 (∃!𝑥𝐴𝑧 ∈ {𝑦𝐵𝜑}𝑥 = 𝑧 / 𝑦𝐶 ↔ ∃!𝑥𝐴𝑦𝐵 (𝜑𝑥 = 𝐶))
3416, 26, 333bitr3g 302 . 2 ((∀𝑧 ∈ {𝑦𝐵𝜑}𝑧 / 𝑦𝐶𝐴 ∧ {𝑦𝐵𝜑} ≠ ∅) → (∃!𝑥𝐴𝑦𝐵 (𝜑𝑥 = 𝐶) ↔ ∃!𝑥𝐴𝑦𝐵 (𝜑𝑥 = 𝐶)))
3514, 15, 34syl2anbr 497 1 ((∀𝑦𝐵 (𝜑𝐶𝐴) ∧ ∃𝑦𝐵 𝜑) → (∃!𝑥𝐴𝑦𝐵 (𝜑𝑥 = 𝐶) ↔ ∃!𝑥𝐴𝑦𝐵 (𝜑𝑥 = 𝐶)))
 Colors of variables: wff setvar class Syntax hints:   → wi 4   ↔ wb 196   ∧ wa 384   = wceq 1482   ∈ wcel 1989   ≠ wne 2793  ∀wral 2911  ∃wrex 2912  ∃!wreu 2913  {crab 2915  ⦋csb 3531  ∅c0 3913 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1721  ax-4 1736  ax-5 1838  ax-6 1887  ax-7 1934  ax-8 1991  ax-9 1998  ax-10 2018  ax-11 2033  ax-12 2046  ax-13 2245  ax-ext 2601  ax-nul 4787  ax-pow 4841 This theorem depends on definitions:  df-bi 197  df-or 385  df-an 386  df-tru 1485  df-ex 1704  df-nf 1709  df-sb 1880  df-eu 2473  df-mo 2474  df-clab 2608  df-cleq 2614  df-clel 2617  df-nfc 2752  df-ne 2794  df-ral 2916  df-rex 2917  df-reu 2918  df-rab 2920  df-v 3200  df-sbc 3434  df-csb 3532  df-dif 3575  df-nul 3914 This theorem is referenced by:  cdleme25dN  35470
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