Theorem rmounid 32841

Description: A case where an "at most one" restricted existential quantifier for a union is equivalent to such a quantifier for one of the sets. (Contributed by Thierry Arnoux, 27-Nov-2023.)

Hypothesis

Ref	Expression
rmounid.1	⊢ ((𝜑 ∧ 𝑥 ∈ 𝐵) → ¬ 𝜓)

Assertion

Ref	Expression
rmounid	⊢ (𝜑 → (∃*𝑥 ∈ (𝐴 ∪ 𝐵)𝜓 ↔ ∃*𝑥 ∈ 𝐴 𝜓))

Distinct variable group:   𝜑,𝑥

Allowed substitution hints:   𝜓(𝑥)   𝐴(𝑥)   𝐵(𝑥)

Proof of Theorem rmounid

Step	Hyp	Ref	Expression
1		rmounid.1	. . . . . . . . . . . 12 ⊢ ((𝜑 ∧ 𝑥 ∈ 𝐵) → ¬ 𝜓)
2	1	ex 417	. . . . . . . . . . 11 ⊢ (𝜑 → (𝑥 ∈ 𝐵 → ¬ 𝜓))
3	2	con2d 135	. . . . . . . . . 10 ⊢ (𝜑 → (𝜓 → ¬ 𝑥 ∈ 𝐵))
4	3	imp 411	. . . . . . . . 9 ⊢ ((𝜑 ∧ 𝜓) → ¬ 𝑥 ∈ 𝐵)
5		biorf 949	. . . . . . . . . 10 ⊢ (¬ 𝑥 ∈ 𝐵 → (𝑥 ∈ 𝐴 ↔ (𝑥 ∈ 𝐵 ∨ 𝑥 ∈ 𝐴)))
6		orcom 883	. . . . . . . . . 10 ⊢ ((𝑥 ∈ 𝐴 ∨ 𝑥 ∈ 𝐵) ↔ (𝑥 ∈ 𝐵 ∨ 𝑥 ∈ 𝐴))
7	5, 6	bitr4di 292	. . . . . . . . 9 ⊢ (¬ 𝑥 ∈ 𝐵 → (𝑥 ∈ 𝐴 ↔ (𝑥 ∈ 𝐴 ∨ 𝑥 ∈ 𝐵)))
8	4, 7	syl 18	. . . . . . . 8 ⊢ ((𝜑 ∧ 𝜓) → (𝑥 ∈ 𝐴 ↔ (𝑥 ∈ 𝐴 ∨ 𝑥 ∈ 𝐵)))
9		elun 4107	. . . . . . . 8 ⊢ (𝑥 ∈ (𝐴 ∪ 𝐵) ↔ (𝑥 ∈ 𝐴 ∨ 𝑥 ∈ 𝐵))
10	8, 9	bitr4di 292	. . . . . . 7 ⊢ ((𝜑 ∧ 𝜓) → (𝑥 ∈ 𝐴 ↔ 𝑥 ∈ (𝐴 ∪ 𝐵)))
11	10	pm5.32da 589	. . . . . 6 ⊢ (𝜑 → ((𝜓 ∧ 𝑥 ∈ 𝐴) ↔ (𝜓 ∧ 𝑥 ∈ (𝐴 ∪ 𝐵))))
12	11	biancomd 468	. . . . 5 ⊢ (𝜑 → ((𝜓 ∧ 𝑥 ∈ 𝐴) ↔ (𝑥 ∈ (𝐴 ∪ 𝐵) ∧ 𝜓)))
13	12	bicomd 226	. . . 4 ⊢ (𝜑 → ((𝑥 ∈ (𝐴 ∪ 𝐵) ∧ 𝜓) ↔ (𝜓 ∧ 𝑥 ∈ 𝐴)))
14	13	biancomd 468	. . 3 ⊢ (𝜑 → ((𝑥 ∈ (𝐴 ∪ 𝐵) ∧ 𝜓) ↔ (𝑥 ∈ 𝐴 ∧ 𝜓)))
15	14	mobidv 2577	. 2 ⊢ (𝜑 → (∃*𝑥(𝑥 ∈ (𝐴 ∪ 𝐵) ∧ 𝜓) ↔ ∃*𝑥(𝑥 ∈ 𝐴 ∧ 𝜓)))
16		df-rmo 3369	. 2 ⊢ (∃*𝑥 ∈ (𝐴 ∪ 𝐵)𝜓 ↔ ∃*𝑥(𝑥 ∈ (𝐴 ∪ 𝐵) ∧ 𝜓))
17		df-rmo 3369	. 2 ⊢ (∃*𝑥 ∈ 𝐴 𝜓 ↔ ∃*𝑥(𝑥 ∈ 𝐴 ∧ 𝜓))
18	15, 16, 17	3bitr4g 317	1 ⊢ (𝜑 → (∃*𝑥 ∈ (𝐴 ∪ 𝐵)𝜓 ↔ ∃*𝑥 ∈ 𝐴 𝜓))

Syntax hints:  ¬ wn 3   → wi 4   ↔ wb 209   ∧ wa 400   ∨ wo 860   ∈ wcel 2143  ∃*wmo 2565  ∃*wrmo 3368   ∪ cun 3903

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1825  ax-4 1839  ax-5 1940  ax-6 1997  ax-7 2038  ax-8 2145  ax-9 2153  ax-ext 2735

This theorem depends on definitions:  df-bi 210  df-an 401  df-or 861  df-tru 1573  df-ex 1810  df-sb 2097  df-mo 2567  df-clab 2742  df-cleq 2755  df-clel 2838  df-rmo 3369  df-v 3457  df-un 3910

This theorem is referenced by:  disjxun0  32919