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Mirrors > Home > ILE Home > Th. List > cbvexh | GIF version |
Description: Rule used to change bound variables, using implicit substitition. (Contributed by NM, 5-Aug-1993.) (Revised by Mario Carneiro, 3-Feb-2015.) |
Ref | Expression |
---|---|
cbvexh.1 | ⊢ (𝜑 → ∀𝑦𝜑) |
cbvexh.2 | ⊢ (𝜓 → ∀𝑥𝜓) |
cbvexh.3 | ⊢ (𝑥 = 𝑦 → (𝜑 ↔ 𝜓)) |
Ref | Expression |
---|---|
cbvexh | ⊢ (∃𝑥𝜑 ↔ ∃𝑦𝜓) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | cbvexh.2 | . . . 4 ⊢ (𝜓 → ∀𝑥𝜓) | |
2 | 1 | hbex 1567 | . . 3 ⊢ (∃𝑦𝜓 → ∀𝑥∃𝑦𝜓) |
3 | cbvexh.1 | . . . . 5 ⊢ (𝜑 → ∀𝑦𝜑) | |
4 | cbvexh.3 | . . . . . . 7 ⊢ (𝑥 = 𝑦 → (𝜑 ↔ 𝜓)) | |
5 | 4 | bicomd 139 | . . . . . 6 ⊢ (𝑥 = 𝑦 → (𝜓 ↔ 𝜑)) |
6 | 5 | equcoms 1634 | . . . . 5 ⊢ (𝑦 = 𝑥 → (𝜓 ↔ 𝜑)) |
7 | 3, 6 | equsex 1656 | . . . 4 ⊢ (∃𝑦(𝑦 = 𝑥 ∧ 𝜓) ↔ 𝜑) |
8 | simpr 108 | . . . . 5 ⊢ ((𝑦 = 𝑥 ∧ 𝜓) → 𝜓) | |
9 | 8 | eximi 1531 | . . . 4 ⊢ (∃𝑦(𝑦 = 𝑥 ∧ 𝜓) → ∃𝑦𝜓) |
10 | 7, 9 | sylbir 133 | . . 3 ⊢ (𝜑 → ∃𝑦𝜓) |
11 | 2, 10 | exlimih 1524 | . 2 ⊢ (∃𝑥𝜑 → ∃𝑦𝜓) |
12 | 3 | hbex 1567 | . . 3 ⊢ (∃𝑥𝜑 → ∀𝑦∃𝑥𝜑) |
13 | 1, 4 | equsex 1656 | . . . 4 ⊢ (∃𝑥(𝑥 = 𝑦 ∧ 𝜑) ↔ 𝜓) |
14 | simpr 108 | . . . . 5 ⊢ ((𝑥 = 𝑦 ∧ 𝜑) → 𝜑) | |
15 | 14 | eximi 1531 | . . . 4 ⊢ (∃𝑥(𝑥 = 𝑦 ∧ 𝜑) → ∃𝑥𝜑) |
16 | 13, 15 | sylbir 133 | . . 3 ⊢ (𝜓 → ∃𝑥𝜑) |
17 | 12, 16 | exlimih 1524 | . 2 ⊢ (∃𝑦𝜓 → ∃𝑥𝜑) |
18 | 11, 17 | impbii 124 | 1 ⊢ (∃𝑥𝜑 ↔ ∃𝑦𝜓) |
Colors of variables: wff set class |
Syntax hints: → wi 4 ∧ wa 102 ↔ wb 103 ∀wal 1282 = wceq 1284 ∃wex 1421 |
This theorem was proved from axioms: ax-1 5 ax-2 6 ax-mp 7 ax-ia1 104 ax-ia2 105 ax-ia3 106 ax-5 1376 ax-7 1377 ax-gen 1378 ax-ie1 1422 ax-ie2 1423 ax-8 1435 ax-4 1440 ax-17 1459 ax-i9 1463 ax-ial 1467 |
This theorem depends on definitions: df-bi 115 |
This theorem is referenced by: cbvex 1679 sb8eh 1776 cbvexv 1836 euf 1946 mopick 2019 |
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