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Mirrors > Home > MPE Home > Th. List > Mathboxes > ichnfimlem1 | Structured version Visualization version GIF version |
Description: Lemma for ichnfimlem3 43672: A substitution of a non-free variable has no effect. Give the distinctor in a form that can be easily eliminiated. (Contributed by Wolf Lammen, 6-Aug-2023.) |
Ref | Expression |
---|---|
ichnfimlem1 | ⊢ ((∀𝑦Ⅎ𝑥𝜑 ∧ ¬ ∀𝑥 𝑥 = 𝑦) → ([𝑎 / 𝑥][𝑏 / 𝑦]𝜑 ↔ [𝑏 / 𝑦]𝜑)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | naev 2065 | . . . 4 ⊢ (¬ ∀𝑥 𝑥 = 𝑦 → ¬ ∀𝑥 𝑥 = 𝑏) | |
2 | nfsb4t 2539 | . . . 4 ⊢ (∀𝑦Ⅎ𝑥𝜑 → (¬ ∀𝑥 𝑥 = 𝑏 → Ⅎ𝑥[𝑏 / 𝑦]𝜑)) | |
3 | 1, 2 | syl5 34 | . . 3 ⊢ (∀𝑦Ⅎ𝑥𝜑 → (¬ ∀𝑥 𝑥 = 𝑦 → Ⅎ𝑥[𝑏 / 𝑦]𝜑)) |
4 | 3 | imp 409 | . 2 ⊢ ((∀𝑦Ⅎ𝑥𝜑 ∧ ¬ ∀𝑥 𝑥 = 𝑦) → Ⅎ𝑥[𝑏 / 𝑦]𝜑) |
5 | sbft 2270 | . 2 ⊢ (Ⅎ𝑥[𝑏 / 𝑦]𝜑 → ([𝑎 / 𝑥][𝑏 / 𝑦]𝜑 ↔ [𝑏 / 𝑦]𝜑)) | |
6 | 4, 5 | syl 17 | 1 ⊢ ((∀𝑦Ⅎ𝑥𝜑 ∧ ¬ ∀𝑥 𝑥 = 𝑦) → ([𝑎 / 𝑥][𝑏 / 𝑦]𝜑 ↔ [𝑏 / 𝑦]𝜑)) |
Colors of variables: wff setvar class |
Syntax hints: ¬ wn 3 → wi 4 ↔ wb 208 ∧ wa 398 ∀wal 1535 Ⅎwnf 1784 [wsb 2069 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1796 ax-4 1810 ax-5 1911 ax-6 1970 ax-7 2015 ax-10 2145 ax-11 2161 ax-12 2177 ax-13 2390 |
This theorem depends on definitions: df-bi 209 df-an 399 df-or 844 df-tru 1540 df-ex 1781 df-nf 1785 df-sb 2070 |
This theorem is referenced by: ichnfimlem3 43672 |
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