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Mirrors > Home > MPE Home > Th. List > 2eu1 | Structured version Visualization version GIF version |
Description: Double existential uniqueness. This theorem shows a condition under which a "naive" definition matches the correct one. (Contributed by NM, 3-Dec-2001.) (Proof shortened by Wolf Lammen, 11-Nov-2019.) |
Ref | Expression |
---|---|
2eu1 | ⊢ (∀𝑥∃*𝑦𝜑 → (∃!𝑥∃!𝑦𝜑 ↔ (∃!𝑥∃𝑦𝜑 ∧ ∃!𝑦∃𝑥𝜑))) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | 2eu2ex 2534 | . . . . 5 ⊢ (∃!𝑥∃!𝑦𝜑 → ∃𝑥∃𝑦𝜑) | |
2 | df-mo 2463 | . . . . . . 7 ⊢ (∃*𝑦𝜑 ↔ (∃𝑦𝜑 → ∃!𝑦𝜑)) | |
3 | 2 | albii 1737 | . . . . . 6 ⊢ (∀𝑥∃*𝑦𝜑 ↔ ∀𝑥(∃𝑦𝜑 → ∃!𝑦𝜑)) |
4 | euim 2511 | . . . . . . 7 ⊢ ((∃𝑥∃𝑦𝜑 ∧ ∀𝑥(∃𝑦𝜑 → ∃!𝑦𝜑)) → (∃!𝑥∃!𝑦𝜑 → ∃!𝑥∃𝑦𝜑)) | |
5 | 4 | ex 449 | . . . . . 6 ⊢ (∃𝑥∃𝑦𝜑 → (∀𝑥(∃𝑦𝜑 → ∃!𝑦𝜑) → (∃!𝑥∃!𝑦𝜑 → ∃!𝑥∃𝑦𝜑))) |
6 | 3, 5 | syl5bi 231 | . . . . 5 ⊢ (∃𝑥∃𝑦𝜑 → (∀𝑥∃*𝑦𝜑 → (∃!𝑥∃!𝑦𝜑 → ∃!𝑥∃𝑦𝜑))) |
7 | 1, 6 | syl 17 | . . . 4 ⊢ (∃!𝑥∃!𝑦𝜑 → (∀𝑥∃*𝑦𝜑 → (∃!𝑥∃!𝑦𝜑 → ∃!𝑥∃𝑦𝜑))) |
8 | 7 | pm2.43b 53 | . . 3 ⊢ (∀𝑥∃*𝑦𝜑 → (∃!𝑥∃!𝑦𝜑 → ∃!𝑥∃𝑦𝜑)) |
9 | 2euswap 2536 | . . . 4 ⊢ (∀𝑥∃*𝑦𝜑 → (∃!𝑥∃𝑦𝜑 → ∃!𝑦∃𝑥𝜑)) | |
10 | 8, 9 | syld 46 | . . 3 ⊢ (∀𝑥∃*𝑦𝜑 → (∃!𝑥∃!𝑦𝜑 → ∃!𝑦∃𝑥𝜑)) |
11 | 8, 10 | jcad 554 | . 2 ⊢ (∀𝑥∃*𝑦𝜑 → (∃!𝑥∃!𝑦𝜑 → (∃!𝑥∃𝑦𝜑 ∧ ∃!𝑦∃𝑥𝜑))) |
12 | 2exeu 2537 | . 2 ⊢ ((∃!𝑥∃𝑦𝜑 ∧ ∃!𝑦∃𝑥𝜑) → ∃!𝑥∃!𝑦𝜑) | |
13 | 11, 12 | impbid1 214 | 1 ⊢ (∀𝑥∃*𝑦𝜑 → (∃!𝑥∃!𝑦𝜑 ↔ (∃!𝑥∃𝑦𝜑 ∧ ∃!𝑦∃𝑥𝜑))) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ↔ wb 195 ∧ wa 383 ∀wal 1473 ∃wex 1695 ∃!weu 2458 ∃*wmo 2459 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1713 ax-4 1728 ax-5 1827 ax-6 1875 ax-7 1922 ax-10 2006 ax-11 2021 ax-12 2034 ax-13 2234 |
This theorem depends on definitions: df-bi 196 df-or 384 df-an 385 df-tru 1478 df-ex 1696 df-nf 1701 df-eu 2462 df-mo 2463 |
This theorem is referenced by: 2eu2 2542 2eu3 2543 2eu5 2545 |
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