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Theorem wl-equsb4 33620
Description: Substitution applied to an atomic wff. The distinctor antecedent is more general than a distinct variable constraint. (Contributed by Wolf Lammen, 26-Jun-2019.)
Assertion
Ref Expression
wl-equsb4 (¬ ∀𝑥 𝑥 = 𝑧 → ([𝑦 / 𝑥]𝑦 = 𝑧𝑦 = 𝑧))

Proof of Theorem wl-equsb4
StepHypRef Expression
1 nfeqf 2434 . . . 4 ((¬ ∀𝑥 𝑥 = 𝑦 ∧ ¬ ∀𝑥 𝑥 = 𝑧) → Ⅎ𝑥 𝑦 = 𝑧)
21ex 449 . . 3 (¬ ∀𝑥 𝑥 = 𝑦 → (¬ ∀𝑥 𝑥 = 𝑧 → Ⅎ𝑥 𝑦 = 𝑧))
3 sbft 2504 . . 3 (Ⅎ𝑥 𝑦 = 𝑧 → ([𝑦 / 𝑥]𝑦 = 𝑧𝑦 = 𝑧))
42, 3syl6com 37 . 2 (¬ ∀𝑥 𝑥 = 𝑧 → (¬ ∀𝑥 𝑥 = 𝑦 → ([𝑦 / 𝑥]𝑦 = 𝑧𝑦 = 𝑧)))
5 sbequ12r 2247 . . . 4 (𝑦 = 𝑥 → ([𝑦 / 𝑥]𝑦 = 𝑧𝑦 = 𝑧))
65equcoms 2090 . . 3 (𝑥 = 𝑦 → ([𝑦 / 𝑥]𝑦 = 𝑧𝑦 = 𝑧))
76sps 2190 . 2 (∀𝑥 𝑥 = 𝑦 → ([𝑦 / 𝑥]𝑦 = 𝑧𝑦 = 𝑧))
84, 7pm2.61d2 172 1 (¬ ∀𝑥 𝑥 = 𝑧 → ([𝑦 / 𝑥]𝑦 = 𝑧𝑦 = 𝑧))
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wi 4  wb 196  wal 1618  wnf 1845  [wsb 2034
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1859  ax-4 1874  ax-5 1976  ax-6 2042  ax-7 2078  ax-10 2156  ax-12 2184  ax-13 2379
This theorem depends on definitions:  df-bi 197  df-or 384  df-an 385  df-tru 1623  df-ex 1842  df-nf 1847  df-sb 2035
This theorem is referenced by: (None)
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