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Theorem dtruOLD 5434
Description: Obsolete proof of dtru 5429 as of 01-Jan-2025. (Contributed by NM, 7-Nov-2006.) Avoid ax-13 2365. (Revised by BJ, 31-May-2019.) Avoid ax-12 2163. (Revised by Rohan Ridenour, 9-Oct-2024.) Use ax-pr 5420 instead of ax-pow 5356. (Revised by BTernaryTau, 3-Dec-2024.) (Proof modification is discouraged.) (New usage is discouraged.)
Assertion
Ref Expression
dtruOLD ¬ ∀𝑥 𝑥 = 𝑦
Distinct variable group:   𝑥,𝑦

Proof of Theorem dtruOLD
Dummy variables 𝑤 𝑧 are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 el 5430 . . . 4 𝑤 𝑥𝑤
2 ax-nul 5299 . . . . 5 𝑧𝑥 ¬ 𝑥𝑧
3 elequ1 2105 . . . . . . 7 (𝑥 = 𝑤 → (𝑥𝑧𝑤𝑧))
43notbid 318 . . . . . 6 (𝑥 = 𝑤 → (¬ 𝑥𝑧 ↔ ¬ 𝑤𝑧))
54spw 2029 . . . . 5 (∀𝑥 ¬ 𝑥𝑧 → ¬ 𝑥𝑧)
62, 5eximii 1831 . . . 4 𝑧 ¬ 𝑥𝑧
7 exdistrv 1951 . . . 4 (∃𝑤𝑧(𝑥𝑤 ∧ ¬ 𝑥𝑧) ↔ (∃𝑤 𝑥𝑤 ∧ ∃𝑧 ¬ 𝑥𝑧))
81, 6, 7mpbir2an 708 . . 3 𝑤𝑧(𝑥𝑤 ∧ ¬ 𝑥𝑧)
9 ax9v2 2111 . . . . . 6 (𝑤 = 𝑧 → (𝑥𝑤𝑥𝑧))
109com12 32 . . . . 5 (𝑥𝑤 → (𝑤 = 𝑧𝑥𝑧))
1110con3dimp 408 . . . 4 ((𝑥𝑤 ∧ ¬ 𝑥𝑧) → ¬ 𝑤 = 𝑧)
12112eximi 1830 . . 3 (∃𝑤𝑧(𝑥𝑤 ∧ ¬ 𝑥𝑧) → ∃𝑤𝑧 ¬ 𝑤 = 𝑧)
13 equequ2 2021 . . . . . . 7 (𝑧 = 𝑦 → (𝑤 = 𝑧𝑤 = 𝑦))
1413notbid 318 . . . . . 6 (𝑧 = 𝑦 → (¬ 𝑤 = 𝑧 ↔ ¬ 𝑤 = 𝑦))
15 ax7v1 2005 . . . . . . . 8 (𝑥 = 𝑤 → (𝑥 = 𝑦𝑤 = 𝑦))
1615con3d 152 . . . . . . 7 (𝑥 = 𝑤 → (¬ 𝑤 = 𝑦 → ¬ 𝑥 = 𝑦))
1716spimevw 1990 . . . . . 6 𝑤 = 𝑦 → ∃𝑥 ¬ 𝑥 = 𝑦)
1814, 17biimtrdi 252 . . . . 5 (𝑧 = 𝑦 → (¬ 𝑤 = 𝑧 → ∃𝑥 ¬ 𝑥 = 𝑦))
19 ax7v1 2005 . . . . . . . 8 (𝑥 = 𝑧 → (𝑥 = 𝑦𝑧 = 𝑦))
2019con3d 152 . . . . . . 7 (𝑥 = 𝑧 → (¬ 𝑧 = 𝑦 → ¬ 𝑥 = 𝑦))
2120spimevw 1990 . . . . . 6 𝑧 = 𝑦 → ∃𝑥 ¬ 𝑥 = 𝑦)
2221a1d 25 . . . . 5 𝑧 = 𝑦 → (¬ 𝑤 = 𝑧 → ∃𝑥 ¬ 𝑥 = 𝑦))
2318, 22pm2.61i 182 . . . 4 𝑤 = 𝑧 → ∃𝑥 ¬ 𝑥 = 𝑦)
2423exlimivv 1927 . . 3 (∃𝑤𝑧 ¬ 𝑤 = 𝑧 → ∃𝑥 ¬ 𝑥 = 𝑦)
258, 12, 24mp2b 10 . 2 𝑥 ¬ 𝑥 = 𝑦
26 exnal 1821 . 2 (∃𝑥 ¬ 𝑥 = 𝑦 ↔ ¬ ∀𝑥 𝑥 = 𝑦)
2725, 26mpbi 229 1 ¬ ∀𝑥 𝑥 = 𝑦
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wi 4  wa 395  wal 1531  wex 1773
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1789  ax-4 1803  ax-5 1905  ax-6 1963  ax-7 2003  ax-8 2100  ax-9 2108  ax-nul 5299  ax-pr 5420
This theorem depends on definitions:  df-bi 206  df-an 396  df-or 845  df-ex 1774
This theorem is referenced by: (None)
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