Theorem onmindif 6405

Description: When its successor is subtracted from a class of ordinal numbers, an ordinal number is less than the minimum of the resulting subclass. (Contributed by NM, 1-Dec-2003.)

Assertion

Ref	Expression
onmindif	⊢ ((𝐴 ⊆ On ∧ 𝐵 ∈ On) → 𝐵 ∈ ∩ (𝐴 ∖ suc 𝐵))

Proof of Theorem onmindif

Dummy variable 𝑥 is distinct from all other variables.

Step	Hyp	Ref	Expression
1		eldif 3915	. . . 4 ⊢ (𝑥 ∈ (𝐴 ∖ suc 𝐵) ↔ (𝑥 ∈ 𝐴 ∧ ¬ 𝑥 ∈ suc 𝐵))
2		ssel2 3932	. . . . . . . . 9 ⊢ ((𝐴 ⊆ On ∧ 𝑥 ∈ 𝐴) → 𝑥 ∈ On)
3		ontri1 6345	. . . . . . . . . . 11 ⊢ ((𝑥 ∈ On ∧ 𝐵 ∈ On) → (𝑥 ⊆ 𝐵 ↔ ¬ 𝐵 ∈ 𝑥))
4		onsssuc 6403	. . . . . . . . . . 11 ⊢ ((𝑥 ∈ On ∧ 𝐵 ∈ On) → (𝑥 ⊆ 𝐵 ↔ 𝑥 ∈ suc 𝐵))
5	3, 4	bitr3d 281	. . . . . . . . . 10 ⊢ ((𝑥 ∈ On ∧ 𝐵 ∈ On) → (¬ 𝐵 ∈ 𝑥 ↔ 𝑥 ∈ suc 𝐵))
6	5	con1bid 355	. . . . . . . . 9 ⊢ ((𝑥 ∈ On ∧ 𝐵 ∈ On) → (¬ 𝑥 ∈ suc 𝐵 ↔ 𝐵 ∈ 𝑥))
7	2, 6	sylan 580	. . . . . . . 8 ⊢ (((𝐴 ⊆ On ∧ 𝑥 ∈ 𝐴) ∧ 𝐵 ∈ On) → (¬ 𝑥 ∈ suc 𝐵 ↔ 𝐵 ∈ 𝑥))
8	7	biimpd 229	. . . . . . 7 ⊢ (((𝐴 ⊆ On ∧ 𝑥 ∈ 𝐴) ∧ 𝐵 ∈ On) → (¬ 𝑥 ∈ suc 𝐵 → 𝐵 ∈ 𝑥))
9	8	exp31 419	. . . . . 6 ⊢ (𝐴 ⊆ On → (𝑥 ∈ 𝐴 → (𝐵 ∈ On → (¬ 𝑥 ∈ suc 𝐵 → 𝐵 ∈ 𝑥))))
10	9	com23 86	. . . . 5 ⊢ (𝐴 ⊆ On → (𝐵 ∈ On → (𝑥 ∈ 𝐴 → (¬ 𝑥 ∈ suc 𝐵 → 𝐵 ∈ 𝑥))))
11	10	imp4b 421	. . . 4 ⊢ ((𝐴 ⊆ On ∧ 𝐵 ∈ On) → ((𝑥 ∈ 𝐴 ∧ ¬ 𝑥 ∈ suc 𝐵) → 𝐵 ∈ 𝑥))
12	1, 11	biimtrid 242	. . 3 ⊢ ((𝐴 ⊆ On ∧ 𝐵 ∈ On) → (𝑥 ∈ (𝐴 ∖ suc 𝐵) → 𝐵 ∈ 𝑥))
13	12	ralrimiv 3120	. 2 ⊢ ((𝐴 ⊆ On ∧ 𝐵 ∈ On) → ∀𝑥 ∈ (𝐴 ∖ suc 𝐵)𝐵 ∈ 𝑥)
14		elintg 4907	. . 3 ⊢ (𝐵 ∈ On → (𝐵 ∈ ∩ (𝐴 ∖ suc 𝐵) ↔ ∀𝑥 ∈ (𝐴 ∖ suc 𝐵)𝐵 ∈ 𝑥))
15	14	adantl 481	. 2 ⊢ ((𝐴 ⊆ On ∧ 𝐵 ∈ On) → (𝐵 ∈ ∩ (𝐴 ∖ suc 𝐵) ↔ ∀𝑥 ∈ (𝐴 ∖ suc 𝐵)𝐵 ∈ 𝑥))
16	13, 15	mpbird 257	1 ⊢ ((𝐴 ⊆ On ∧ 𝐵 ∈ On) → 𝐵 ∈ ∩ (𝐴 ∖ suc 𝐵))

Syntax hints:  ¬ wn 3   → wi 4   ↔ wb 206   ∧ wa 395   ∈ wcel 2109  ∀wral 3044   ∖ cdif 3902   ⊆ wss 3905  ∩ cint 4899  Oncon0 6311  suc csuc 6313

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1795  ax-4 1809  ax-5 1910  ax-6 1967  ax-7 2008  ax-8 2111  ax-9 2119  ax-ext 2701  ax-sep 5238  ax-nul 5248  ax-pr 5374

This theorem depends on definitions:  df-bi 207  df-an 396  df-or 848  df-3or 1087  df-3an 1088  df-tru 1543  df-fal 1553  df-ex 1780  df-sb 2066  df-clab 2708  df-cleq 2721  df-clel 2803  df-ne 2926  df-ral 3045  df-rex 3054  df-rab 3397  df-v 3440  df-dif 3908  df-un 3910  df-in 3912  df-ss 3922  df-pss 3925  df-nul 4287  df-if 4479  df-pw 4555  df-sn 4580  df-pr 4582  df-op 4586  df-uni 4862  df-int 4900  df-br 5096  df-opab 5158  df-tr 5203  df-eprel 5523  df-po 5531  df-so 5532  df-fr 5576  df-we 5578  df-ord 6314  df-on 6315  df-suc 6317

This theorem is referenced by:  unblem3  9199  fin23lem26  10238  inaex  44270