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Theorem 2mo 2550
 Description: Two equivalent expressions for double "at most one." (Contributed by NM, 2-Feb-2005.) (Revised by Mario Carneiro, 17-Oct-2016.) (Proof shortened by Wolf Lammen, 2-Nov-2019.)
Assertion
Ref Expression
2mo (∃𝑧𝑤𝑥𝑦(𝜑 → (𝑥 = 𝑧𝑦 = 𝑤)) ↔ ∀𝑥𝑦𝑧𝑤((𝜑 ∧ [𝑧 / 𝑥][𝑤 / 𝑦]𝜑) → (𝑥 = 𝑧𝑦 = 𝑤)))
Distinct variable groups:   𝑥,𝑦,𝑧,𝑤   𝜑,𝑧,𝑤
Allowed substitution hints:   𝜑(𝑥,𝑦)

Proof of Theorem 2mo
StepHypRef Expression
1 2mo2 2549 . . . 4 ((∃*𝑥𝑦𝜑 ∧ ∃*𝑦𝑥𝜑) ↔ ∃𝑧𝑤𝑥𝑦(𝜑 → (𝑥 = 𝑧𝑦 = 𝑤)))
2 nfmo1 2480 . . . . . . 7 𝑥∃*𝑥𝑦𝜑
3 nfe1 2024 . . . . . . . 8 𝑥𝑥𝜑
43nfmo 2486 . . . . . . 7 𝑥∃*𝑦𝑥𝜑
52, 4nfan 1825 . . . . . 6 𝑥(∃*𝑥𝑦𝜑 ∧ ∃*𝑦𝑥𝜑)
6 nfe1 2024 . . . . . . . . 9 𝑦𝑦𝜑
76nfmo 2486 . . . . . . . 8 𝑦∃*𝑥𝑦𝜑
8 nfmo1 2480 . . . . . . . 8 𝑦∃*𝑦𝑥𝜑
97, 8nfan 1825 . . . . . . 7 𝑦(∃*𝑥𝑦𝜑 ∧ ∃*𝑦𝑥𝜑)
10 19.8a 2049 . . . . . . . . 9 (𝜑 → ∃𝑦𝜑)
11 spsbe 1881 . . . . . . . . . 10 ([𝑤 / 𝑦]𝜑 → ∃𝑦𝜑)
1211sbimi 1883 . . . . . . . . 9 ([𝑧 / 𝑥][𝑤 / 𝑦]𝜑 → [𝑧 / 𝑥]∃𝑦𝜑)
13 nfv 1840 . . . . . . . . . . . 12 𝑧𝑦𝜑
1413mo3 2506 . . . . . . . . . . 11 (∃*𝑥𝑦𝜑 ↔ ∀𝑥𝑧((∃𝑦𝜑 ∧ [𝑧 / 𝑥]∃𝑦𝜑) → 𝑥 = 𝑧))
1514biimpi 206 . . . . . . . . . 10 (∃*𝑥𝑦𝜑 → ∀𝑥𝑧((∃𝑦𝜑 ∧ [𝑧 / 𝑥]∃𝑦𝜑) → 𝑥 = 𝑧))
161519.21bbi 2058 . . . . . . . . 9 (∃*𝑥𝑦𝜑 → ((∃𝑦𝜑 ∧ [𝑧 / 𝑥]∃𝑦𝜑) → 𝑥 = 𝑧))
1710, 12, 16syl2ani 687 . . . . . . . 8 (∃*𝑥𝑦𝜑 → ((𝜑 ∧ [𝑧 / 𝑥][𝑤 / 𝑦]𝜑) → 𝑥 = 𝑧))
18 19.8a 2049 . . . . . . . . 9 (𝜑 → ∃𝑥𝜑)
19 sbcom2 2444 . . . . . . . . . 10 ([𝑧 / 𝑥][𝑤 / 𝑦]𝜑 ↔ [𝑤 / 𝑦][𝑧 / 𝑥]𝜑)
20 spsbe 1881 . . . . . . . . . . 11 ([𝑧 / 𝑥]𝜑 → ∃𝑥𝜑)
2120sbimi 1883 . . . . . . . . . 10 ([𝑤 / 𝑦][𝑧 / 𝑥]𝜑 → [𝑤 / 𝑦]∃𝑥𝜑)
2219, 21sylbi 207 . . . . . . . . 9 ([𝑧 / 𝑥][𝑤 / 𝑦]𝜑 → [𝑤 / 𝑦]∃𝑥𝜑)
23 nfv 1840 . . . . . . . . . . . 12 𝑤𝑥𝜑
2423mo3 2506 . . . . . . . . . . 11 (∃*𝑦𝑥𝜑 ↔ ∀𝑦𝑤((∃𝑥𝜑 ∧ [𝑤 / 𝑦]∃𝑥𝜑) → 𝑦 = 𝑤))
2524biimpi 206 . . . . . . . . . 10 (∃*𝑦𝑥𝜑 → ∀𝑦𝑤((∃𝑥𝜑 ∧ [𝑤 / 𝑦]∃𝑥𝜑) → 𝑦 = 𝑤))
262519.21bbi 2058 . . . . . . . . 9 (∃*𝑦𝑥𝜑 → ((∃𝑥𝜑 ∧ [𝑤 / 𝑦]∃𝑥𝜑) → 𝑦 = 𝑤))
2718, 22, 26syl2ani 687 . . . . . . . 8 (∃*𝑦𝑥𝜑 → ((𝜑 ∧ [𝑧 / 𝑥][𝑤 / 𝑦]𝜑) → 𝑦 = 𝑤))
2817, 27anim12ii 593 . . . . . . 7 ((∃*𝑥𝑦𝜑 ∧ ∃*𝑦𝑥𝜑) → ((𝜑 ∧ [𝑧 / 𝑥][𝑤 / 𝑦]𝜑) → (𝑥 = 𝑧𝑦 = 𝑤)))
299, 28alrimi 2080 . . . . . 6 ((∃*𝑥𝑦𝜑 ∧ ∃*𝑦𝑥𝜑) → ∀𝑦((𝜑 ∧ [𝑧 / 𝑥][𝑤 / 𝑦]𝜑) → (𝑥 = 𝑧𝑦 = 𝑤)))
305, 29alrimi 2080 . . . . 5 ((∃*𝑥𝑦𝜑 ∧ ∃*𝑦𝑥𝜑) → ∀𝑥𝑦((𝜑 ∧ [𝑧 / 𝑥][𝑤 / 𝑦]𝜑) → (𝑥 = 𝑧𝑦 = 𝑤)))
3130alrimivv 1853 . . . 4 ((∃*𝑥𝑦𝜑 ∧ ∃*𝑦𝑥𝜑) → ∀𝑧𝑤𝑥𝑦((𝜑 ∧ [𝑧 / 𝑥][𝑤 / 𝑦]𝜑) → (𝑥 = 𝑧𝑦 = 𝑤)))
321, 31sylbir 225 . . 3 (∃𝑧𝑤𝑥𝑦(𝜑 → (𝑥 = 𝑧𝑦 = 𝑤)) → ∀𝑧𝑤𝑥𝑦((𝜑 ∧ [𝑧 / 𝑥][𝑤 / 𝑦]𝜑) → (𝑥 = 𝑧𝑦 = 𝑤)))
33 nfs1v 2436 . . . . . . . 8 𝑥[𝑧 / 𝑥][𝑤 / 𝑦]𝜑
34 nfs1v 2436 . . . . . . . . . 10 𝑦[𝑤 / 𝑦]𝜑
3534nfsb 2439 . . . . . . . . 9 𝑦[𝑧 / 𝑥][𝑤 / 𝑦]𝜑
36 pm3.21 464 . . . . . . . . . 10 ([𝑧 / 𝑥][𝑤 / 𝑦]𝜑 → (𝜑 → (𝜑 ∧ [𝑧 / 𝑥][𝑤 / 𝑦]𝜑)))
3736imim1d 82 . . . . . . . . 9 ([𝑧 / 𝑥][𝑤 / 𝑦]𝜑 → (((𝜑 ∧ [𝑧 / 𝑥][𝑤 / 𝑦]𝜑) → (𝑥 = 𝑧𝑦 = 𝑤)) → (𝜑 → (𝑥 = 𝑧𝑦 = 𝑤))))
3835, 37alimd 2079 . . . . . . . 8 ([𝑧 / 𝑥][𝑤 / 𝑦]𝜑 → (∀𝑦((𝜑 ∧ [𝑧 / 𝑥][𝑤 / 𝑦]𝜑) → (𝑥 = 𝑧𝑦 = 𝑤)) → ∀𝑦(𝜑 → (𝑥 = 𝑧𝑦 = 𝑤))))
3933, 38alimd 2079 . . . . . . 7 ([𝑧 / 𝑥][𝑤 / 𝑦]𝜑 → (∀𝑥𝑦((𝜑 ∧ [𝑧 / 𝑥][𝑤 / 𝑦]𝜑) → (𝑥 = 𝑧𝑦 = 𝑤)) → ∀𝑥𝑦(𝜑 → (𝑥 = 𝑧𝑦 = 𝑤))))
4039com12 32 . . . . . 6 (∀𝑥𝑦((𝜑 ∧ [𝑧 / 𝑥][𝑤 / 𝑦]𝜑) → (𝑥 = 𝑧𝑦 = 𝑤)) → ([𝑧 / 𝑥][𝑤 / 𝑦]𝜑 → ∀𝑥𝑦(𝜑 → (𝑥 = 𝑧𝑦 = 𝑤))))
4140aleximi 1756 . . . . 5 (∀𝑤𝑥𝑦((𝜑 ∧ [𝑧 / 𝑥][𝑤 / 𝑦]𝜑) → (𝑥 = 𝑧𝑦 = 𝑤)) → (∃𝑤[𝑧 / 𝑥][𝑤 / 𝑦]𝜑 → ∃𝑤𝑥𝑦(𝜑 → (𝑥 = 𝑧𝑦 = 𝑤))))
4241aleximi 1756 . . . 4 (∀𝑧𝑤𝑥𝑦((𝜑 ∧ [𝑧 / 𝑥][𝑤 / 𝑦]𝜑) → (𝑥 = 𝑧𝑦 = 𝑤)) → (∃𝑧𝑤[𝑧 / 𝑥][𝑤 / 𝑦]𝜑 → ∃𝑧𝑤𝑥𝑦(𝜑 → (𝑥 = 𝑧𝑦 = 𝑤))))
43 2nexaln 1754 . . . . . 6 (¬ ∃𝑥𝑦𝜑 ↔ ∀𝑥𝑦 ¬ 𝜑)
44 2sb8e 2466 . . . . . 6 (∃𝑥𝑦𝜑 ↔ ∃𝑧𝑤[𝑧 / 𝑥][𝑤 / 𝑦]𝜑)
4543, 44xchnxbi 322 . . . . 5 (¬ ∃𝑧𝑤[𝑧 / 𝑥][𝑤 / 𝑦]𝜑 ↔ ∀𝑥𝑦 ¬ 𝜑)
46 pm2.21 120 . . . . . . . . 9 𝜑 → (𝜑 → (𝑥 = 𝑧𝑦 = 𝑤)))
47462alimi 1737 . . . . . . . 8 (∀𝑥𝑦 ¬ 𝜑 → ∀𝑥𝑦(𝜑 → (𝑥 = 𝑧𝑦 = 𝑤)))
48472eximi 1760 . . . . . . 7 (∃𝑧𝑤𝑥𝑦 ¬ 𝜑 → ∃𝑧𝑤𝑥𝑦(𝜑 → (𝑥 = 𝑧𝑦 = 𝑤)))
494819.23bi 2059 . . . . . 6 (∃𝑤𝑥𝑦 ¬ 𝜑 → ∃𝑧𝑤𝑥𝑦(𝜑 → (𝑥 = 𝑧𝑦 = 𝑤)))
504919.23bi 2059 . . . . 5 (∀𝑥𝑦 ¬ 𝜑 → ∃𝑧𝑤𝑥𝑦(𝜑 → (𝑥 = 𝑧𝑦 = 𝑤)))
5145, 50sylbi 207 . . . 4 (¬ ∃𝑧𝑤[𝑧 / 𝑥][𝑤 / 𝑦]𝜑 → ∃𝑧𝑤𝑥𝑦(𝜑 → (𝑥 = 𝑧𝑦 = 𝑤)))
5242, 51pm2.61d1 171 . . 3 (∀𝑧𝑤𝑥𝑦((𝜑 ∧ [𝑧 / 𝑥][𝑤 / 𝑦]𝜑) → (𝑥 = 𝑧𝑦 = 𝑤)) → ∃𝑧𝑤𝑥𝑦(𝜑 → (𝑥 = 𝑧𝑦 = 𝑤)))
5332, 52impbii 199 . 2 (∃𝑧𝑤𝑥𝑦(𝜑 → (𝑥 = 𝑧𝑦 = 𝑤)) ↔ ∀𝑧𝑤𝑥𝑦((𝜑 ∧ [𝑧 / 𝑥][𝑤 / 𝑦]𝜑) → (𝑥 = 𝑧𝑦 = 𝑤)))
54 alrot4 2036 . 2 (∀𝑧𝑤𝑥𝑦((𝜑 ∧ [𝑧 / 𝑥][𝑤 / 𝑦]𝜑) → (𝑥 = 𝑧𝑦 = 𝑤)) ↔ ∀𝑥𝑦𝑧𝑤((𝜑 ∧ [𝑧 / 𝑥][𝑤 / 𝑦]𝜑) → (𝑥 = 𝑧𝑦 = 𝑤)))
5553, 54bitri 264 1 (∃𝑧𝑤𝑥𝑦(𝜑 → (𝑥 = 𝑧𝑦 = 𝑤)) ↔ ∀𝑥𝑦𝑧𝑤((𝜑 ∧ [𝑧 / 𝑥][𝑤 / 𝑦]𝜑) → (𝑥 = 𝑧𝑦 = 𝑤)))
 Colors of variables: wff setvar class Syntax hints:  ¬ wn 3   → wi 4   ↔ wb 196   ∧ wa 384  ∀wal 1478  ∃wex 1701  [wsb 1877  ∃*wmo 2470 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1719  ax-4 1734  ax-5 1836  ax-6 1885  ax-7 1932  ax-10 2016  ax-11 2031  ax-12 2044  ax-13 2245 This theorem depends on definitions:  df-bi 197  df-or 385  df-an 386  df-tru 1483  df-ex 1702  df-nf 1707  df-sb 1878  df-eu 2473  df-mo 2474 This theorem is referenced by:  2mos  2551
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