Theorem unidif0 4164

Description: The removal of the empty set from a class does not affect its union. (Contributed by NM, 22-Mar-2004.)

Assertion

Ref	Expression
unidif0	⊢ ∪ (𝐴 ∖ {∅}) = ∪ 𝐴

Proof of Theorem unidif0

Dummy variables 𝑥 𝑦 are mutually distinct and distinct from all other variables.

Step	Hyp	Ref	Expression
1		n0i 3428	. . . . . . 7 ⊢ (𝑥 ∈ 𝑦 → ¬ 𝑦 = ∅)
2	1	pm4.71i 391	. . . . . 6 ⊢ (𝑥 ∈ 𝑦 ↔ (𝑥 ∈ 𝑦 ∧ ¬ 𝑦 = ∅))
3	2	anbi1i 458	. . . . 5 ⊢ ((𝑥 ∈ 𝑦 ∧ 𝑦 ∈ 𝐴) ↔ ((𝑥 ∈ 𝑦 ∧ ¬ 𝑦 = ∅) ∧ 𝑦 ∈ 𝐴))
4		an32 562	. . . . 5 ⊢ (((𝑥 ∈ 𝑦 ∧ 𝑦 ∈ 𝐴) ∧ ¬ 𝑦 = ∅) ↔ ((𝑥 ∈ 𝑦 ∧ ¬ 𝑦 = ∅) ∧ 𝑦 ∈ 𝐴))
5		anass 401	. . . . 5 ⊢ (((𝑥 ∈ 𝑦 ∧ 𝑦 ∈ 𝐴) ∧ ¬ 𝑦 = ∅) ↔ (𝑥 ∈ 𝑦 ∧ (𝑦 ∈ 𝐴 ∧ ¬ 𝑦 = ∅)))
6	3, 4, 5	3bitr2ri 209	. . . 4 ⊢ ((𝑥 ∈ 𝑦 ∧ (𝑦 ∈ 𝐴 ∧ ¬ 𝑦 = ∅)) ↔ (𝑥 ∈ 𝑦 ∧ 𝑦 ∈ 𝐴))
7	6	exbii 1605	. . 3 ⊢ (∃𝑦(𝑥 ∈ 𝑦 ∧ (𝑦 ∈ 𝐴 ∧ ¬ 𝑦 = ∅)) ↔ ∃𝑦(𝑥 ∈ 𝑦 ∧ 𝑦 ∈ 𝐴))
8		eluni 3810	. . . 4 ⊢ (𝑥 ∈ ∪ (𝐴 ∖ {∅}) ↔ ∃𝑦(𝑥 ∈ 𝑦 ∧ 𝑦 ∈ (𝐴 ∖ {∅})))
9		eldif 3138	. . . . . . 7 ⊢ (𝑦 ∈ (𝐴 ∖ {∅}) ↔ (𝑦 ∈ 𝐴 ∧ ¬ 𝑦 ∈ {∅}))
10		velsn 3608	. . . . . . . . 9 ⊢ (𝑦 ∈ {∅} ↔ 𝑦 = ∅)
11	10	notbii 668	. . . . . . . 8 ⊢ (¬ 𝑦 ∈ {∅} ↔ ¬ 𝑦 = ∅)
12	11	anbi2i 457	. . . . . . 7 ⊢ ((𝑦 ∈ 𝐴 ∧ ¬ 𝑦 ∈ {∅}) ↔ (𝑦 ∈ 𝐴 ∧ ¬ 𝑦 = ∅))
13	9, 12	bitri 184	. . . . . 6 ⊢ (𝑦 ∈ (𝐴 ∖ {∅}) ↔ (𝑦 ∈ 𝐴 ∧ ¬ 𝑦 = ∅))
14	13	anbi2i 457	. . . . 5 ⊢ ((𝑥 ∈ 𝑦 ∧ 𝑦 ∈ (𝐴 ∖ {∅})) ↔ (𝑥 ∈ 𝑦 ∧ (𝑦 ∈ 𝐴 ∧ ¬ 𝑦 = ∅)))
15	14	exbii 1605	. . . 4 ⊢ (∃𝑦(𝑥 ∈ 𝑦 ∧ 𝑦 ∈ (𝐴 ∖ {∅})) ↔ ∃𝑦(𝑥 ∈ 𝑦 ∧ (𝑦 ∈ 𝐴 ∧ ¬ 𝑦 = ∅)))
16	8, 15	bitri 184	. . 3 ⊢ (𝑥 ∈ ∪ (𝐴 ∖ {∅}) ↔ ∃𝑦(𝑥 ∈ 𝑦 ∧ (𝑦 ∈ 𝐴 ∧ ¬ 𝑦 = ∅)))
17		eluni 3810	. . 3 ⊢ (𝑥 ∈ ∪ 𝐴 ↔ ∃𝑦(𝑥 ∈ 𝑦 ∧ 𝑦 ∈ 𝐴))
18	7, 16, 17	3bitr4i 212	. 2 ⊢ (𝑥 ∈ ∪ (𝐴 ∖ {∅}) ↔ 𝑥 ∈ ∪ 𝐴)
19	18	eqriv 2174	1 ⊢ ∪ (𝐴 ∖ {∅}) = ∪ 𝐴

Syntax hints:  ¬ wn 3   ∧ wa 104   = wceq 1353  ∃wex 1492   ∈ wcel 2148   ∖ cdif 3126  ∅c0 3422  {csn 3591  ∪ cuni 3807

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-in1 614  ax-in2 615  ax-io 709  ax-5 1447  ax-7 1448  ax-gen 1449  ax-ie1 1493  ax-ie2 1494  ax-8 1504  ax-10 1505  ax-11 1506  ax-i12 1507  ax-bndl 1509  ax-4 1510  ax-17 1526  ax-i9 1530  ax-ial 1534  ax-i5r 1535  ax-ext 2159

This theorem depends on definitions:  df-bi 117  df-tru 1356  df-nf 1461  df-sb 1763  df-clab 2164  df-cleq 2170  df-clel 2173  df-nfc 2308  df-v 2739  df-dif 3131  df-nul 3423  df-sn 3597  df-uni 3808

This theorem is referenced by: (None)