Theorem onelss 5766

Description: An element of an ordinal number is a subset of the number. (Contributed by NM, 5-Jun-1994.) (Proof shortened by Andrew Salmon, 25-Jul-2011.)

Assertion

Ref	Expression
onelss	⊢ (𝐴 ∈ On → (𝐵 ∈ 𝐴 → 𝐵 ⊆ 𝐴))

Proof of Theorem onelss

Step	Hyp	Ref	Expression
1		eloni 5733	. 2 ⊢ (𝐴 ∈ On → Ord 𝐴)
2		ordelss 5739	. . 3 ⊢ ((Ord 𝐴 ∧ 𝐵 ∈ 𝐴) → 𝐵 ⊆ 𝐴)
3	2	ex 450	. 2 ⊢ (Ord 𝐴 → (𝐵 ∈ 𝐴 → 𝐵 ⊆ 𝐴))
4	1, 3	syl 17	1 ⊢ (𝐴 ∈ On → (𝐵 ∈ 𝐴 → 𝐵 ⊆ 𝐴))

Syntax hints:   → wi 4   ∈ wcel 1990   ⊆ wss 3574  Ord word 5722  Oncon0 5723

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1722  ax-4 1737  ax-5 1839  ax-6 1888  ax-7 1935  ax-9 1999  ax-10 2019  ax-11 2034  ax-12 2047  ax-13 2246  ax-ext 2602

This theorem depends on definitions:  df-bi 197  df-or 385  df-an 386  df-tru 1486  df-ex 1705  df-nf 1710  df-sb 1881  df-clab 2609  df-cleq 2615  df-clel 2618  df-nfc 2753  df-ral 2917  df-rex 2918  df-v 3202  df-in 3581  df-ss 3588  df-uni 4437  df-tr 4753  df-po 5035  df-so 5036  df-fr 5073  df-we 5075  df-ord 5726  df-on 5727

This theorem is referenced by:  ordunidif  5773  onelssi  5836  ssorduni  6985  suceloni  7013  tfisi  7058  tfrlem9  7481  tfrlem11  7484  oaordex  7638  oaass  7641  odi  7659  omass  7660  oewordri  7672  nnaordex  7718  domtriord  8106  hartogs  8449  card2on  8459  tskwe  8776  infxpenlem  8836  cfub  9071  cfsuc  9079  coflim  9083  hsmexlem2  9249  ondomon  9385  pwcfsdom  9405  inar1  9597  tskord  9602  grudomon  9639  gruina  9640  dfrdg2  31701  poseq  31750  sltres  31815  nosupno  31849  aomclem6  37629