Theorem infdiffi 9579

Description: Removing a finite set from an infinite set does not change the cardinality of the set. (Contributed by Mario Carneiro, 30-Apr-2015.)

Assertion

Ref	Expression
infdiffi	⊢ ((ω ≼ 𝐴 ∧ 𝐵 ∈ Fin) → (𝐴 ∖ 𝐵) ≈ 𝐴)

Proof of Theorem infdiffi

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

Step	Hyp	Ref	Expression
1		difeq2 4060	. . . . . 6 ⊢ (𝑥 = ∅ → (𝐴 ∖ 𝑥) = (𝐴 ∖ ∅))
2		dif0 4318	. . . . . 6 ⊢ (𝐴 ∖ ∅) = 𝐴
3	1, 2	eqtrdi 2787	. . . . 5 ⊢ (𝑥 = ∅ → (𝐴 ∖ 𝑥) = 𝐴)
4	3	breq1d 5095	. . . 4 ⊢ (𝑥 = ∅ → ((𝐴 ∖ 𝑥) ≈ 𝐴 ↔ 𝐴 ≈ 𝐴))
5	4	imbi2d 340	. . 3 ⊢ (𝑥 = ∅ → ((ω ≼ 𝐴 → (𝐴 ∖ 𝑥) ≈ 𝐴) ↔ (ω ≼ 𝐴 → 𝐴 ≈ 𝐴)))
6		difeq2 4060	. . . . 5 ⊢ (𝑥 = 𝑦 → (𝐴 ∖ 𝑥) = (𝐴 ∖ 𝑦))
7	6	breq1d 5095	. . . 4 ⊢ (𝑥 = 𝑦 → ((𝐴 ∖ 𝑥) ≈ 𝐴 ↔ (𝐴 ∖ 𝑦) ≈ 𝐴))
8	7	imbi2d 340	. . 3 ⊢ (𝑥 = 𝑦 → ((ω ≼ 𝐴 → (𝐴 ∖ 𝑥) ≈ 𝐴) ↔ (ω ≼ 𝐴 → (𝐴 ∖ 𝑦) ≈ 𝐴)))
9		difeq2 4060	. . . . . 6 ⊢ (𝑥 = (𝑦 ∪ {𝑧}) → (𝐴 ∖ 𝑥) = (𝐴 ∖ (𝑦 ∪ {𝑧})))
10		difun1 4239	. . . . . 6 ⊢ (𝐴 ∖ (𝑦 ∪ {𝑧})) = ((𝐴 ∖ 𝑦) ∖ {𝑧})
11	9, 10	eqtrdi 2787	. . . . 5 ⊢ (𝑥 = (𝑦 ∪ {𝑧}) → (𝐴 ∖ 𝑥) = ((𝐴 ∖ 𝑦) ∖ {𝑧}))
12	11	breq1d 5095	. . . 4 ⊢ (𝑥 = (𝑦 ∪ {𝑧}) → ((𝐴 ∖ 𝑥) ≈ 𝐴 ↔ ((𝐴 ∖ 𝑦) ∖ {𝑧}) ≈ 𝐴))
13	12	imbi2d 340	. . 3 ⊢ (𝑥 = (𝑦 ∪ {𝑧}) → ((ω ≼ 𝐴 → (𝐴 ∖ 𝑥) ≈ 𝐴) ↔ (ω ≼ 𝐴 → ((𝐴 ∖ 𝑦) ∖ {𝑧}) ≈ 𝐴)))
14		difeq2 4060	. . . . 5 ⊢ (𝑥 = 𝐵 → (𝐴 ∖ 𝑥) = (𝐴 ∖ 𝐵))
15	14	breq1d 5095	. . . 4 ⊢ (𝑥 = 𝐵 → ((𝐴 ∖ 𝑥) ≈ 𝐴 ↔ (𝐴 ∖ 𝐵) ≈ 𝐴))
16	15	imbi2d 340	. . 3 ⊢ (𝑥 = 𝐵 → ((ω ≼ 𝐴 → (𝐴 ∖ 𝑥) ≈ 𝐴) ↔ (ω ≼ 𝐴 → (𝐴 ∖ 𝐵) ≈ 𝐴)))
17		reldom 8899	. . . . 5 ⊢ Rel ≼
18	17	brrelex2i 5688	. . . 4 ⊢ (ω ≼ 𝐴 → 𝐴 ∈ V)
19		enrefg 8931	. . . 4 ⊢ (𝐴 ∈ V → 𝐴 ≈ 𝐴)
20	18, 19	syl 17	. . 3 ⊢ (ω ≼ 𝐴 → 𝐴 ≈ 𝐴)
21		domen2 9058	. . . . . . . . 9 ⊢ ((𝐴 ∖ 𝑦) ≈ 𝐴 → (ω ≼ (𝐴 ∖ 𝑦) ↔ ω ≼ 𝐴))
22	21	biimparc 479	. . . . . . . 8 ⊢ ((ω ≼ 𝐴 ∧ (𝐴 ∖ 𝑦) ≈ 𝐴) → ω ≼ (𝐴 ∖ 𝑦))
23		infdifsn 9578	. . . . . . . 8 ⊢ (ω ≼ (𝐴 ∖ 𝑦) → ((𝐴 ∖ 𝑦) ∖ {𝑧}) ≈ (𝐴 ∖ 𝑦))
24	22, 23	syl 17	. . . . . . 7 ⊢ ((ω ≼ 𝐴 ∧ (𝐴 ∖ 𝑦) ≈ 𝐴) → ((𝐴 ∖ 𝑦) ∖ {𝑧}) ≈ (𝐴 ∖ 𝑦))
25		entr 8953	. . . . . . 7 ⊢ ((((𝐴 ∖ 𝑦) ∖ {𝑧}) ≈ (𝐴 ∖ 𝑦) ∧ (𝐴 ∖ 𝑦) ≈ 𝐴) → ((𝐴 ∖ 𝑦) ∖ {𝑧}) ≈ 𝐴)
26	24, 25	sylancom 589	. . . . . 6 ⊢ ((ω ≼ 𝐴 ∧ (𝐴 ∖ 𝑦) ≈ 𝐴) → ((𝐴 ∖ 𝑦) ∖ {𝑧}) ≈ 𝐴)
27	26	ex 412	. . . . 5 ⊢ (ω ≼ 𝐴 → ((𝐴 ∖ 𝑦) ≈ 𝐴 → ((𝐴 ∖ 𝑦) ∖ {𝑧}) ≈ 𝐴))
28	27	a2i 14	. . . 4 ⊢ ((ω ≼ 𝐴 → (𝐴 ∖ 𝑦) ≈ 𝐴) → (ω ≼ 𝐴 → ((𝐴 ∖ 𝑦) ∖ {𝑧}) ≈ 𝐴))
29	28	a1i 11	. . 3 ⊢ (𝑦 ∈ Fin → ((ω ≼ 𝐴 → (𝐴 ∖ 𝑦) ≈ 𝐴) → (ω ≼ 𝐴 → ((𝐴 ∖ 𝑦) ∖ {𝑧}) ≈ 𝐴)))
30	5, 8, 13, 16, 20, 29	findcard2 9099	. 2 ⊢ (𝐵 ∈ Fin → (ω ≼ 𝐴 → (𝐴 ∖ 𝐵) ≈ 𝐴))
31	30	impcom 407	1 ⊢ ((ω ≼ 𝐴 ∧ 𝐵 ∈ Fin) → (𝐴 ∖ 𝐵) ≈ 𝐴)

Syntax hints:   → wi 4   ∧ wa 395   = wceq 1542   ∈ wcel 2114  Vcvv 3429   ∖ cdif 3886   ∪ cun 3887  ∅c0 4273  {csn 4567   class class class wbr 5085  ωcom 7817   ≈ cen 8890   ≼ cdom 8891  Fincfn 8893

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1797  ax-4 1811  ax-5 1912  ax-6 1969  ax-7 2010  ax-8 2116  ax-9 2124  ax-10 2147  ax-11 2163  ax-12 2185  ax-ext 2708  ax-sep 5231  ax-nul 5241  ax-pow 5307  ax-pr 5375  ax-un 7689

This theorem depends on definitions:  df-bi 207  df-an 396  df-or 849  df-3or 1088  df-3an 1089  df-tru 1545  df-fal 1555  df-ex 1782  df-nf 1786  df-sb 2069  df-mo 2539  df-eu 2569  df-clab 2715  df-cleq 2728  df-clel 2811  df-nfc 2885  df-ne 2933  df-ral 3052  df-rex 3062  df-reu 3343  df-rab 3390  df-v 3431  df-sbc 3729  df-csb 3838  df-dif 3892  df-un 3894  df-in 3896  df-ss 3906  df-pss 3909  df-nul 4274  df-if 4467  df-pw 4543  df-sn 4568  df-pr 4570  df-op 4574  df-uni 4851  df-br 5086  df-opab 5148  df-mpt 5167  df-tr 5193  df-id 5526  df-eprel 5531  df-po 5539  df-so 5540  df-fr 5584  df-we 5586  df-xp 5637  df-rel 5638  df-cnv 5639  df-co 5640  df-dm 5641  df-rn 5642  df-res 5643  df-ima 5644  df-ord 6326  df-on 6327  df-lim 6328  df-suc 6329  df-iota 6454  df-fun 6500  df-fn 6501  df-f 6502  df-f1 6503  df-fo 6504  df-f1o 6505  df-fv 6506  df-om 7818  df-er 8643  df-en 8894  df-dom 8895  df-fin 8897

This theorem is referenced by: (None)