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Mirrors > Home > ILE Home > Th. List > ceqsex2 | GIF version |
Description: Elimination of two existential quantifiers, using implicit substitution. (Contributed by Scott Fenton, 7-Jun-2006.) |
Ref | Expression |
---|---|
ceqsex2.1 | ⊢ Ⅎ𝑥𝜓 |
ceqsex2.2 | ⊢ Ⅎ𝑦𝜒 |
ceqsex2.3 | ⊢ 𝐴 ∈ V |
ceqsex2.4 | ⊢ 𝐵 ∈ V |
ceqsex2.5 | ⊢ (𝑥 = 𝐴 → (𝜑 ↔ 𝜓)) |
ceqsex2.6 | ⊢ (𝑦 = 𝐵 → (𝜓 ↔ 𝜒)) |
Ref | Expression |
---|---|
ceqsex2 | ⊢ (∃𝑥∃𝑦(𝑥 = 𝐴 ∧ 𝑦 = 𝐵 ∧ 𝜑) ↔ 𝜒) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | 3anass 984 | . . . . 5 ⊢ ((𝑥 = 𝐴 ∧ 𝑦 = 𝐵 ∧ 𝜑) ↔ (𝑥 = 𝐴 ∧ (𝑦 = 𝐵 ∧ 𝜑))) | |
2 | 1 | exbii 1616 | . . . 4 ⊢ (∃𝑦(𝑥 = 𝐴 ∧ 𝑦 = 𝐵 ∧ 𝜑) ↔ ∃𝑦(𝑥 = 𝐴 ∧ (𝑦 = 𝐵 ∧ 𝜑))) |
3 | 19.42v 1918 | . . . 4 ⊢ (∃𝑦(𝑥 = 𝐴 ∧ (𝑦 = 𝐵 ∧ 𝜑)) ↔ (𝑥 = 𝐴 ∧ ∃𝑦(𝑦 = 𝐵 ∧ 𝜑))) | |
4 | 2, 3 | bitri 184 | . . 3 ⊢ (∃𝑦(𝑥 = 𝐴 ∧ 𝑦 = 𝐵 ∧ 𝜑) ↔ (𝑥 = 𝐴 ∧ ∃𝑦(𝑦 = 𝐵 ∧ 𝜑))) |
5 | 4 | exbii 1616 | . 2 ⊢ (∃𝑥∃𝑦(𝑥 = 𝐴 ∧ 𝑦 = 𝐵 ∧ 𝜑) ↔ ∃𝑥(𝑥 = 𝐴 ∧ ∃𝑦(𝑦 = 𝐵 ∧ 𝜑))) |
6 | nfv 1539 | . . . . 5 ⊢ Ⅎ𝑥 𝑦 = 𝐵 | |
7 | ceqsex2.1 | . . . . 5 ⊢ Ⅎ𝑥𝜓 | |
8 | 6, 7 | nfan 1576 | . . . 4 ⊢ Ⅎ𝑥(𝑦 = 𝐵 ∧ 𝜓) |
9 | 8 | nfex 1648 | . . 3 ⊢ Ⅎ𝑥∃𝑦(𝑦 = 𝐵 ∧ 𝜓) |
10 | ceqsex2.3 | . . 3 ⊢ 𝐴 ∈ V | |
11 | ceqsex2.5 | . . . . 5 ⊢ (𝑥 = 𝐴 → (𝜑 ↔ 𝜓)) | |
12 | 11 | anbi2d 464 | . . . 4 ⊢ (𝑥 = 𝐴 → ((𝑦 = 𝐵 ∧ 𝜑) ↔ (𝑦 = 𝐵 ∧ 𝜓))) |
13 | 12 | exbidv 1836 | . . 3 ⊢ (𝑥 = 𝐴 → (∃𝑦(𝑦 = 𝐵 ∧ 𝜑) ↔ ∃𝑦(𝑦 = 𝐵 ∧ 𝜓))) |
14 | 9, 10, 13 | ceqsex 2790 | . 2 ⊢ (∃𝑥(𝑥 = 𝐴 ∧ ∃𝑦(𝑦 = 𝐵 ∧ 𝜑)) ↔ ∃𝑦(𝑦 = 𝐵 ∧ 𝜓)) |
15 | ceqsex2.2 | . . 3 ⊢ Ⅎ𝑦𝜒 | |
16 | ceqsex2.4 | . . 3 ⊢ 𝐵 ∈ V | |
17 | ceqsex2.6 | . . 3 ⊢ (𝑦 = 𝐵 → (𝜓 ↔ 𝜒)) | |
18 | 15, 16, 17 | ceqsex 2790 | . 2 ⊢ (∃𝑦(𝑦 = 𝐵 ∧ 𝜓) ↔ 𝜒) |
19 | 5, 14, 18 | 3bitri 206 | 1 ⊢ (∃𝑥∃𝑦(𝑥 = 𝐴 ∧ 𝑦 = 𝐵 ∧ 𝜑) ↔ 𝜒) |
Colors of variables: wff set class |
Syntax hints: → wi 4 ∧ wa 104 ↔ wb 105 ∧ w3a 980 = wceq 1364 Ⅎwnf 1471 ∃wex 1503 ∈ wcel 2160 Vcvv 2752 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-ia1 106 ax-ia2 107 ax-ia3 108 ax-5 1458 ax-7 1459 ax-gen 1460 ax-ie1 1504 ax-ie2 1505 ax-8 1515 ax-4 1521 ax-17 1537 ax-i9 1541 ax-ial 1545 ax-ext 2171 |
This theorem depends on definitions: df-bi 117 df-3an 982 df-nf 1472 df-sb 1774 df-clab 2176 df-cleq 2182 df-clel 2185 df-v 2754 |
This theorem is referenced by: ceqsex2v 2793 |
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