Theorem onsucssi 7578

Description: A set belongs to an ordinal number iff its successor is a subset of the ordinal number. Exercise 8 of [TakeutiZaring] p. 42 and its converse. (Contributed by NM, 16-Sep-1995.)

Hypotheses

Ref	Expression
onssi.1	⊢ 𝐴 ∈ On
onsucssi.2	⊢ 𝐵 ∈ On

Assertion

Ref	Expression
onsucssi	⊢ (𝐴 ∈ 𝐵 ↔ suc 𝐴 ⊆ 𝐵)

Proof of Theorem onsucssi

Step	Hyp	Ref	Expression
1		onssi.1	. 2 ⊢ 𝐴 ∈ On
2		onsucssi.2	. . 3 ⊢ 𝐵 ∈ On
3	2	onordi 6278	. 2 ⊢ Ord 𝐵
4		ordelsuc 7557	. 2 ⊢ ((𝐴 ∈ On ∧ Ord 𝐵) → (𝐴 ∈ 𝐵 ↔ suc 𝐴 ⊆ 𝐵))
5	1, 3, 4	mp2an 692	1 ⊢ (𝐴 ∈ 𝐵 ↔ suc 𝐴 ⊆ 𝐵)

Syntax hints:   ↔ wb 209   ∈ wcel 2114   ⊆ wss 3844  Ord word 6172  Oncon0 6173  suc csuc 6175

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1802  ax-4 1816  ax-5 1917  ax-6 1975  ax-7 2020  ax-8 2116  ax-9 2124  ax-11 2162  ax-ext 2711  ax-sep 5168  ax-nul 5175  ax-pr 5297  ax-un 7482

This theorem depends on definitions:  df-bi 210  df-an 400  df-or 847  df-3or 1089  df-3an 1090  df-tru 1545  df-fal 1555  df-ex 1787  df-sb 2075  df-clab 2718  df-cleq 2731  df-clel 2812  df-ne 2936  df-ral 3059  df-rex 3060  df-rab 3063  df-v 3401  df-dif 3847  df-un 3849  df-in 3851  df-ss 3861  df-pss 3863  df-nul 4213  df-if 4416  df-sn 4518  df-pr 4520  df-tp 4522  df-op 4524  df-uni 4798  df-br 5032  df-opab 5094  df-tr 5138  df-eprel 5435  df-po 5443  df-so 5444  df-fr 5484  df-we 5486  df-ord 6176  df-on 6177  df-suc 6179

This theorem is referenced by:  omopthlem1  8316  rankval4  9372  rankc1  9375  rankc2  9376  rankxplim  9384  rankxplim3  9386  onsucsuccmpi  34278