Theorem reu2 2780

Description: A way to express restricted uniqueness. (Contributed by NM, 22-Nov-1994.)

Assertion

Ref	Expression
reu2	⊢ (∃!𝑥 ∈ 𝐴 𝜑 ↔ (∃𝑥 ∈ 𝐴 𝜑 ∧ ∀𝑥 ∈ 𝐴 ∀𝑦 ∈ 𝐴 ((𝜑 ∧ [𝑦 / 𝑥]𝜑) → 𝑥 = 𝑦)))

Distinct variable groups:   𝑥,𝑦,𝐴   𝜑,𝑦

Allowed substitution hint:   𝜑(𝑥)

Proof of Theorem reu2

Step	Hyp	Ref	Expression
1		nfv 1461	. . 3 ⊢ Ⅎ𝑦(𝑥 ∈ 𝐴 ∧ 𝜑)
2	1	eu2 1985	. 2 ⊢ (∃!𝑥(𝑥 ∈ 𝐴 ∧ 𝜑) ↔ (∃𝑥(𝑥 ∈ 𝐴 ∧ 𝜑) ∧ ∀𝑥∀𝑦(((𝑥 ∈ 𝐴 ∧ 𝜑) ∧ [𝑦 / 𝑥](𝑥 ∈ 𝐴 ∧ 𝜑)) → 𝑥 = 𝑦)))
3		df-reu 2355	. 2 ⊢ (∃!𝑥 ∈ 𝐴 𝜑 ↔ ∃!𝑥(𝑥 ∈ 𝐴 ∧ 𝜑))
4		df-rex 2354	. . 3 ⊢ (∃𝑥 ∈ 𝐴 𝜑 ↔ ∃𝑥(𝑥 ∈ 𝐴 ∧ 𝜑))
5		df-ral 2353	. . . 4 ⊢ (∀𝑥 ∈ 𝐴 ∀𝑦 ∈ 𝐴 ((𝜑 ∧ [𝑦 / 𝑥]𝜑) → 𝑥 = 𝑦) ↔ ∀𝑥(𝑥 ∈ 𝐴 → ∀𝑦 ∈ 𝐴 ((𝜑 ∧ [𝑦 / 𝑥]𝜑) → 𝑥 = 𝑦)))
6		19.21v 1794	. . . . . 6 ⊢ (∀𝑦(𝑥 ∈ 𝐴 → (𝑦 ∈ 𝐴 → ((𝜑 ∧ [𝑦 / 𝑥]𝜑) → 𝑥 = 𝑦))) ↔ (𝑥 ∈ 𝐴 → ∀𝑦(𝑦 ∈ 𝐴 → ((𝜑 ∧ [𝑦 / 𝑥]𝜑) → 𝑥 = 𝑦))))
7		nfv 1461	. . . . . . . . . . . . 13 ⊢ Ⅎ𝑥 𝑦 ∈ 𝐴
8		nfs1v 1856	. . . . . . . . . . . . 13 ⊢ Ⅎ𝑥[𝑦 / 𝑥]𝜑
9	7, 8	nfan 1497	. . . . . . . . . . . 12 ⊢ Ⅎ𝑥(𝑦 ∈ 𝐴 ∧ [𝑦 / 𝑥]𝜑)
10		eleq1 2141	. . . . . . . . . . . . 13 ⊢ (𝑥 = 𝑦 → (𝑥 ∈ 𝐴 ↔ 𝑦 ∈ 𝐴))
11		sbequ12 1694	. . . . . . . . . . . . 13 ⊢ (𝑥 = 𝑦 → (𝜑 ↔ [𝑦 / 𝑥]𝜑))
12	10, 11	anbi12d 456	. . . . . . . . . . . 12 ⊢ (𝑥 = 𝑦 → ((𝑥 ∈ 𝐴 ∧ 𝜑) ↔ (𝑦 ∈ 𝐴 ∧ [𝑦 / 𝑥]𝜑)))
13	9, 12	sbie 1714	. . . . . . . . . . 11 ⊢ ([𝑦 / 𝑥](𝑥 ∈ 𝐴 ∧ 𝜑) ↔ (𝑦 ∈ 𝐴 ∧ [𝑦 / 𝑥]𝜑))
14	13	anbi2i 444	. . . . . . . . . 10 ⊢ (((𝑥 ∈ 𝐴 ∧ 𝜑) ∧ [𝑦 / 𝑥](𝑥 ∈ 𝐴 ∧ 𝜑)) ↔ ((𝑥 ∈ 𝐴 ∧ 𝜑) ∧ (𝑦 ∈ 𝐴 ∧ [𝑦 / 𝑥]𝜑)))
15		an4 550	. . . . . . . . . 10 ⊢ (((𝑥 ∈ 𝐴 ∧ 𝜑) ∧ (𝑦 ∈ 𝐴 ∧ [𝑦 / 𝑥]𝜑)) ↔ ((𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐴) ∧ (𝜑 ∧ [𝑦 / 𝑥]𝜑)))
16	14, 15	bitri 182	. . . . . . . . 9 ⊢ (((𝑥 ∈ 𝐴 ∧ 𝜑) ∧ [𝑦 / 𝑥](𝑥 ∈ 𝐴 ∧ 𝜑)) ↔ ((𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐴) ∧ (𝜑 ∧ [𝑦 / 𝑥]𝜑)))
17	16	imbi1i 236	. . . . . . . 8 ⊢ ((((𝑥 ∈ 𝐴 ∧ 𝜑) ∧ [𝑦 / 𝑥](𝑥 ∈ 𝐴 ∧ 𝜑)) → 𝑥 = 𝑦) ↔ (((𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐴) ∧ (𝜑 ∧ [𝑦 / 𝑥]𝜑)) → 𝑥 = 𝑦))
18		impexp 259	. . . . . . . 8 ⊢ ((((𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐴) ∧ (𝜑 ∧ [𝑦 / 𝑥]𝜑)) → 𝑥 = 𝑦) ↔ ((𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐴) → ((𝜑 ∧ [𝑦 / 𝑥]𝜑) → 𝑥 = 𝑦)))
19		impexp 259	. . . . . . . 8 ⊢ (((𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐴) → ((𝜑 ∧ [𝑦 / 𝑥]𝜑) → 𝑥 = 𝑦)) ↔ (𝑥 ∈ 𝐴 → (𝑦 ∈ 𝐴 → ((𝜑 ∧ [𝑦 / 𝑥]𝜑) → 𝑥 = 𝑦))))
20	17, 18, 19	3bitri 204	. . . . . . 7 ⊢ ((((𝑥 ∈ 𝐴 ∧ 𝜑) ∧ [𝑦 / 𝑥](𝑥 ∈ 𝐴 ∧ 𝜑)) → 𝑥 = 𝑦) ↔ (𝑥 ∈ 𝐴 → (𝑦 ∈ 𝐴 → ((𝜑 ∧ [𝑦 / 𝑥]𝜑) → 𝑥 = 𝑦))))
21	20	albii 1399	. . . . . 6 ⊢ (∀𝑦(((𝑥 ∈ 𝐴 ∧ 𝜑) ∧ [𝑦 / 𝑥](𝑥 ∈ 𝐴 ∧ 𝜑)) → 𝑥 = 𝑦) ↔ ∀𝑦(𝑥 ∈ 𝐴 → (𝑦 ∈ 𝐴 → ((𝜑 ∧ [𝑦 / 𝑥]𝜑) → 𝑥 = 𝑦))))
22		df-ral 2353	. . . . . . 7 ⊢ (∀𝑦 ∈ 𝐴 ((𝜑 ∧ [𝑦 / 𝑥]𝜑) → 𝑥 = 𝑦) ↔ ∀𝑦(𝑦 ∈ 𝐴 → ((𝜑 ∧ [𝑦 / 𝑥]𝜑) → 𝑥 = 𝑦)))
23	22	imbi2i 224	. . . . . 6 ⊢ ((𝑥 ∈ 𝐴 → ∀𝑦 ∈ 𝐴 ((𝜑 ∧ [𝑦 / 𝑥]𝜑) → 𝑥 = 𝑦)) ↔ (𝑥 ∈ 𝐴 → ∀𝑦(𝑦 ∈ 𝐴 → ((𝜑 ∧ [𝑦 / 𝑥]𝜑) → 𝑥 = 𝑦))))
24	6, 21, 23	3bitr4i 210	. . . . 5 ⊢ (∀𝑦(((𝑥 ∈ 𝐴 ∧ 𝜑) ∧ [𝑦 / 𝑥](𝑥 ∈ 𝐴 ∧ 𝜑)) → 𝑥 = 𝑦) ↔ (𝑥 ∈ 𝐴 → ∀𝑦 ∈ 𝐴 ((𝜑 ∧ [𝑦 / 𝑥]𝜑) → 𝑥 = 𝑦)))
25	24	albii 1399	. . . 4 ⊢ (∀𝑥∀𝑦(((𝑥 ∈ 𝐴 ∧ 𝜑) ∧ [𝑦 / 𝑥](𝑥 ∈ 𝐴 ∧ 𝜑)) → 𝑥 = 𝑦) ↔ ∀𝑥(𝑥 ∈ 𝐴 → ∀𝑦 ∈ 𝐴 ((𝜑 ∧ [𝑦 / 𝑥]𝜑) → 𝑥 = 𝑦)))
26	5, 25	bitr4i 185	. . 3 ⊢ (∀𝑥 ∈ 𝐴 ∀𝑦 ∈ 𝐴 ((𝜑 ∧ [𝑦 / 𝑥]𝜑) → 𝑥 = 𝑦) ↔ ∀𝑥∀𝑦(((𝑥 ∈ 𝐴 ∧ 𝜑) ∧ [𝑦 / 𝑥](𝑥 ∈ 𝐴 ∧ 𝜑)) → 𝑥 = 𝑦))
27	4, 26	anbi12i 447	. 2 ⊢ ((∃𝑥 ∈ 𝐴 𝜑 ∧ ∀𝑥 ∈ 𝐴 ∀𝑦 ∈ 𝐴 ((𝜑 ∧ [𝑦 / 𝑥]𝜑) → 𝑥 = 𝑦)) ↔ (∃𝑥(𝑥 ∈ 𝐴 ∧ 𝜑) ∧ ∀𝑥∀𝑦(((𝑥 ∈ 𝐴 ∧ 𝜑) ∧ [𝑦 / 𝑥](𝑥 ∈ 𝐴 ∧ 𝜑)) → 𝑥 = 𝑦)))
28	2, 3, 27	3bitr4i 210	1 ⊢ (∃!𝑥 ∈ 𝐴 𝜑 ↔ (∃𝑥 ∈ 𝐴 𝜑 ∧ ∀𝑥 ∈ 𝐴 ∀𝑦 ∈ 𝐴 ((𝜑 ∧ [𝑦 / 𝑥]𝜑) → 𝑥 = 𝑦)))

Syntax hints:   → wi 4   ∧ wa 102   ↔ wb 103  ∀wal 1282  ∃wex 1421   ∈ wcel 1433  [wsb 1685  ∃!weu 1941  ∀wral 2348  ∃wrex 2349  ∃!wreu 2350

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-io 662  ax-5 1376  ax-7 1377  ax-gen 1378  ax-ie1 1422  ax-ie2 1423  ax-8 1435  ax-10 1436  ax-11 1437  ax-i12 1438  ax-bndl 1439  ax-4 1440  ax-17 1459  ax-i9 1463  ax-ial 1467  ax-i5r 1468  ax-ext 2063

This theorem depends on definitions:  df-bi 115  df-nf 1390  df-sb 1686  df-eu 1944  df-cleq 2074  df-clel 2077  df-ral 2353  df-rex 2354  df-reu 2355

This theorem is referenced by: (None)