Metamath Proof Explorer |
< Previous
Next >
Nearby theorems |
||
Mirrors > Home > MPE Home > Th. List > eu1 | Structured version Visualization version GIF version |
Description: An alternate way to express uniqueness used by some authors. Exercise 2(b) of [Margaris] p. 110. (Contributed by NM, 20-Aug-1993.) (Revised by Mario Carneiro, 7-Oct-2016.) (Proof shortened by Wolf Lammen, 29-Oct-2018.) |
Ref | Expression |
---|---|
eu1.1 | ⊢ Ⅎ𝑦𝜑 |
Ref | Expression |
---|---|
eu1 | ⊢ (∃!𝑥𝜑 ↔ ∃𝑥(𝜑 ∧ ∀𝑦([𝑦 / 𝑥]𝜑 → 𝑥 = 𝑦))) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | nfs1v 2425 | . . 3 ⊢ Ⅎ𝑥[𝑦 / 𝑥]𝜑 | |
2 | 1 | euf 2466 | . 2 ⊢ (∃!𝑦[𝑦 / 𝑥]𝜑 ↔ ∃𝑥∀𝑦([𝑦 / 𝑥]𝜑 ↔ 𝑦 = 𝑥)) |
3 | eu1.1 | . . 3 ⊢ Ⅎ𝑦𝜑 | |
4 | 3 | sb8eu 2491 | . 2 ⊢ (∃!𝑥𝜑 ↔ ∃!𝑦[𝑦 / 𝑥]𝜑) |
5 | 3 | sb6rf 2411 | . . . . 5 ⊢ (𝜑 ↔ ∀𝑦(𝑦 = 𝑥 → [𝑦 / 𝑥]𝜑)) |
6 | equcom 1932 | . . . . . . 7 ⊢ (𝑥 = 𝑦 ↔ 𝑦 = 𝑥) | |
7 | 6 | imbi2i 325 | . . . . . 6 ⊢ (([𝑦 / 𝑥]𝜑 → 𝑥 = 𝑦) ↔ ([𝑦 / 𝑥]𝜑 → 𝑦 = 𝑥)) |
8 | 7 | albii 1737 | . . . . 5 ⊢ (∀𝑦([𝑦 / 𝑥]𝜑 → 𝑥 = 𝑦) ↔ ∀𝑦([𝑦 / 𝑥]𝜑 → 𝑦 = 𝑥)) |
9 | 5, 8 | anbi12ci 730 | . . . 4 ⊢ ((𝜑 ∧ ∀𝑦([𝑦 / 𝑥]𝜑 → 𝑥 = 𝑦)) ↔ (∀𝑦([𝑦 / 𝑥]𝜑 → 𝑦 = 𝑥) ∧ ∀𝑦(𝑦 = 𝑥 → [𝑦 / 𝑥]𝜑))) |
10 | albiim 1806 | . . . 4 ⊢ (∀𝑦([𝑦 / 𝑥]𝜑 ↔ 𝑦 = 𝑥) ↔ (∀𝑦([𝑦 / 𝑥]𝜑 → 𝑦 = 𝑥) ∧ ∀𝑦(𝑦 = 𝑥 → [𝑦 / 𝑥]𝜑))) | |
11 | 9, 10 | bitr4i 266 | . . 3 ⊢ ((𝜑 ∧ ∀𝑦([𝑦 / 𝑥]𝜑 → 𝑥 = 𝑦)) ↔ ∀𝑦([𝑦 / 𝑥]𝜑 ↔ 𝑦 = 𝑥)) |
12 | 11 | exbii 1764 | . 2 ⊢ (∃𝑥(𝜑 ∧ ∀𝑦([𝑦 / 𝑥]𝜑 → 𝑥 = 𝑦)) ↔ ∃𝑥∀𝑦([𝑦 / 𝑥]𝜑 ↔ 𝑦 = 𝑥)) |
13 | 2, 4, 12 | 3bitr4i 291 | 1 ⊢ (∃!𝑥𝜑 ↔ ∃𝑥(𝜑 ∧ ∀𝑦([𝑦 / 𝑥]𝜑 → 𝑥 = 𝑦))) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ↔ wb 195 ∧ wa 383 ∀wal 1473 ∃wex 1695 Ⅎwnf 1699 [wsb 1867 ∃!weu 2458 |
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-sb 1868 df-eu 2462 |
This theorem is referenced by: euexALT 2499 kmlem15 8869 |
Copyright terms: Public domain | W3C validator |