Theorem eueq2 3706

Description: Equality has existential uniqueness (split into 2 cases). (Contributed by NM, 5-Apr-1995.)

Hypotheses

Ref	Expression
eueq2.1	⊢ 𝐴 ∈ V
eueq2.2	⊢ 𝐵 ∈ V

Assertion

Ref	Expression
eueq2	⊢ ∃!𝑥((𝜑 ∧ 𝑥 = 𝐴) ∨ (¬ 𝜑 ∧ 𝑥 = 𝐵))

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

Proof of Theorem eueq2

Step	Hyp	Ref	Expression
1		notnot 142	. . . 4 ⊢ (𝜑 → ¬ ¬ 𝜑)
2		eueq2.1	. . . . . 6 ⊢ 𝐴 ∈ V
3	2	eueqi 3705	. . . . 5 ⊢ ∃!𝑥 𝑥 = 𝐴
4		euanv 2621	. . . . . 6 ⊢ (∃!𝑥(𝜑 ∧ 𝑥 = 𝐴) ↔ (𝜑 ∧ ∃!𝑥 𝑥 = 𝐴))
5	4	biimpri 227	. . . . 5 ⊢ ((𝜑 ∧ ∃!𝑥 𝑥 = 𝐴) → ∃!𝑥(𝜑 ∧ 𝑥 = 𝐴))
6	3, 5	mpan2 690	. . . 4 ⊢ (𝜑 → ∃!𝑥(𝜑 ∧ 𝑥 = 𝐴))
7		euorv 2609	. . . 4 ⊢ ((¬ ¬ 𝜑 ∧ ∃!𝑥(𝜑 ∧ 𝑥 = 𝐴)) → ∃!𝑥(¬ 𝜑 ∨ (𝜑 ∧ 𝑥 = 𝐴)))
8	1, 6, 7	syl2anc 585	. . 3 ⊢ (𝜑 → ∃!𝑥(¬ 𝜑 ∨ (𝜑 ∧ 𝑥 = 𝐴)))
9		orcom 869	. . . . 5 ⊢ ((¬ 𝜑 ∨ (𝜑 ∧ 𝑥 = 𝐴)) ↔ ((𝜑 ∧ 𝑥 = 𝐴) ∨ ¬ 𝜑))
10	1	bianfd 536	. . . . . 6 ⊢ (𝜑 → (¬ 𝜑 ↔ (¬ 𝜑 ∧ 𝑥 = 𝐵)))
11	10	orbi2d 915	. . . . 5 ⊢ (𝜑 → (((𝜑 ∧ 𝑥 = 𝐴) ∨ ¬ 𝜑) ↔ ((𝜑 ∧ 𝑥 = 𝐴) ∨ (¬ 𝜑 ∧ 𝑥 = 𝐵))))
12	9, 11	bitrid 283	. . . 4 ⊢ (𝜑 → ((¬ 𝜑 ∨ (𝜑 ∧ 𝑥 = 𝐴)) ↔ ((𝜑 ∧ 𝑥 = 𝐴) ∨ (¬ 𝜑 ∧ 𝑥 = 𝐵))))
13	12	eubidv 2581	. . 3 ⊢ (𝜑 → (∃!𝑥(¬ 𝜑 ∨ (𝜑 ∧ 𝑥 = 𝐴)) ↔ ∃!𝑥((𝜑 ∧ 𝑥 = 𝐴) ∨ (¬ 𝜑 ∧ 𝑥 = 𝐵))))
14	8, 13	mpbid 231	. 2 ⊢ (𝜑 → ∃!𝑥((𝜑 ∧ 𝑥 = 𝐴) ∨ (¬ 𝜑 ∧ 𝑥 = 𝐵)))
15		eueq2.2	. . . . . 6 ⊢ 𝐵 ∈ V
16	15	eueqi 3705	. . . . 5 ⊢ ∃!𝑥 𝑥 = 𝐵
17		euanv 2621	. . . . . 6 ⊢ (∃!𝑥(¬ 𝜑 ∧ 𝑥 = 𝐵) ↔ (¬ 𝜑 ∧ ∃!𝑥 𝑥 = 𝐵))
18	17	biimpri 227	. . . . 5 ⊢ ((¬ 𝜑 ∧ ∃!𝑥 𝑥 = 𝐵) → ∃!𝑥(¬ 𝜑 ∧ 𝑥 = 𝐵))
19	16, 18	mpan2 690	. . . 4 ⊢ (¬ 𝜑 → ∃!𝑥(¬ 𝜑 ∧ 𝑥 = 𝐵))
20		euorv 2609	. . . 4 ⊢ ((¬ 𝜑 ∧ ∃!𝑥(¬ 𝜑 ∧ 𝑥 = 𝐵)) → ∃!𝑥(𝜑 ∨ (¬ 𝜑 ∧ 𝑥 = 𝐵)))
21	19, 20	mpdan 686	. . 3 ⊢ (¬ 𝜑 → ∃!𝑥(𝜑 ∨ (¬ 𝜑 ∧ 𝑥 = 𝐵)))
22		id 22	. . . . . 6 ⊢ (¬ 𝜑 → ¬ 𝜑)
23	22	bianfd 536	. . . . 5 ⊢ (¬ 𝜑 → (𝜑 ↔ (𝜑 ∧ 𝑥 = 𝐴)))
24	23	orbi1d 916	. . . 4 ⊢ (¬ 𝜑 → ((𝜑 ∨ (¬ 𝜑 ∧ 𝑥 = 𝐵)) ↔ ((𝜑 ∧ 𝑥 = 𝐴) ∨ (¬ 𝜑 ∧ 𝑥 = 𝐵))))
25	24	eubidv 2581	. . 3 ⊢ (¬ 𝜑 → (∃!𝑥(𝜑 ∨ (¬ 𝜑 ∧ 𝑥 = 𝐵)) ↔ ∃!𝑥((𝜑 ∧ 𝑥 = 𝐴) ∨ (¬ 𝜑 ∧ 𝑥 = 𝐵))))
26	21, 25	mpbid 231	. 2 ⊢ (¬ 𝜑 → ∃!𝑥((𝜑 ∧ 𝑥 = 𝐴) ∨ (¬ 𝜑 ∧ 𝑥 = 𝐵)))
27	14, 26	pm2.61i 182	1 ⊢ ∃!𝑥((𝜑 ∧ 𝑥 = 𝐴) ∨ (¬ 𝜑 ∧ 𝑥 = 𝐵))

Syntax hints:  ¬ wn 3   ∧ wa 397   ∨ wo 846   = wceq 1542   ∈ wcel 2107  ∃!weu 2563  Vcvv 3475

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1798  ax-4 1812  ax-5 1914  ax-6 1972  ax-7 2012  ax-8 2109  ax-9 2117  ax-ext 2704

This theorem depends on definitions:  df-bi 206  df-an 398  df-or 847  df-tru 1545  df-ex 1783  df-sb 2069  df-mo 2535  df-eu 2564  df-clab 2711  df-cleq 2725  df-clel 2811  df-v 3477

This theorem is referenced by: (None)