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Theorem wl-mo2t 33684
Description: Closed form of mo2 2626. (Contributed by Wolf Lammen, 18-Aug-2019.)
Assertion
Ref Expression
wl-mo2t (∀𝑥𝑦𝜑 → (∃*𝑥𝜑 ↔ ∃𝑦𝑥(𝜑𝑥 = 𝑦)))
Distinct variable group:   𝑥,𝑦
Allowed substitution hints:   𝜑(𝑥,𝑦)

Proof of Theorem wl-mo2t
Dummy variable 𝑢 is distinct from all other variables.
StepHypRef Expression
1 mo2v 2624 . 2 (∃*𝑥𝜑 ↔ ∃𝑢𝑥(𝜑𝑥 = 𝑢))
2 nfnf1 2186 . . . 4 𝑦𝑦𝜑
32nfal 2316 . . 3 𝑦𝑥𝑦𝜑
4 nfa1 2183 . . . 4 𝑥𝑥𝑦𝜑
5 sp 2206 . . . . 5 (∀𝑥𝑦𝜑 → Ⅎ𝑦𝜑)
6 nfvd 1995 . . . . 5 (∀𝑥𝑦𝜑 → Ⅎ𝑦 𝑥 = 𝑢)
75, 6nfimd 1972 . . . 4 (∀𝑥𝑦𝜑 → Ⅎ𝑦(𝜑𝑥 = 𝑢))
84, 7nfald 2326 . . 3 (∀𝑥𝑦𝜑 → Ⅎ𝑦𝑥(𝜑𝑥 = 𝑢))
9 equequ2 2110 . . . . . 6 (𝑢 = 𝑦 → (𝑥 = 𝑢𝑥 = 𝑦))
109imbi2d 329 . . . . 5 (𝑢 = 𝑦 → ((𝜑𝑥 = 𝑢) ↔ (𝜑𝑥 = 𝑦)))
1110albidv 2000 . . . 4 (𝑢 = 𝑦 → (∀𝑥(𝜑𝑥 = 𝑢) ↔ ∀𝑥(𝜑𝑥 = 𝑦)))
1211a1i 11 . . 3 (∀𝑥𝑦𝜑 → (𝑢 = 𝑦 → (∀𝑥(𝜑𝑥 = 𝑢) ↔ ∀𝑥(𝜑𝑥 = 𝑦))))
133, 8, 12cbvexd 2436 . 2 (∀𝑥𝑦𝜑 → (∃𝑢𝑥(𝜑𝑥 = 𝑢) ↔ ∃𝑦𝑥(𝜑𝑥 = 𝑦)))
141, 13syl5bb 272 1 (∀𝑥𝑦𝜑 → (∃*𝑥𝜑 ↔ ∃𝑦𝑥(𝜑𝑥 = 𝑦)))
Colors of variables: wff setvar class
Syntax hints:  wi 4  wb 196  wal 1628  wex 1851  wnf 1855  ∃*wmo 2618
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1869  ax-4 1884  ax-5 1990  ax-6 2056  ax-7 2092  ax-10 2173  ax-11 2189  ax-12 2202  ax-13 2407
This theorem depends on definitions:  df-bi 197  df-an 383  df-or 827  df-ex 1852  df-nf 1857  df-eu 2621  df-mo 2622
This theorem is referenced by:  wl-mo3t  33685
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