Theorem trssord 6367

Description: A transitive subclass of an ordinal class is ordinal. (Contributed by NM, 29-May-1994.)

Assertion

Ref	Expression
trssord	⊢ ((Tr 𝐴 ∧ 𝐴 ⊆ 𝐵 ∧ Ord 𝐵) → Ord 𝐴)

Proof of Theorem trssord

Step	Hyp	Ref	Expression
1		wess 5638	. . . . 5 ⊢ (𝐴 ⊆ 𝐵 → ( E We 𝐵 → E We 𝐴))
2		ordwe 6363	. . . . 5 ⊢ (Ord 𝐵 → E We 𝐵)
3	1, 2	impel 514	. . . 4 ⊢ ((𝐴 ⊆ 𝐵 ∧ Ord 𝐵) → E We 𝐴)
4	3	anim2i 628	. . 3 ⊢ ((Tr 𝐴 ∧ (𝐴 ⊆ 𝐵 ∧ Ord 𝐵)) → (Tr 𝐴 ∧ E We 𝐴))
5	4	3impb 1130	. 2 ⊢ ((Tr 𝐴 ∧ 𝐴 ⊆ 𝐵 ∧ Ord 𝐵) → (Tr 𝐴 ∧ E We 𝐴))
6		df-ord 6353	. 2 ⊢ (Ord 𝐴 ↔ (Tr 𝐴 ∧ E We 𝐴))
7	5, 6	sylibr 237	1 ⊢ ((Tr 𝐴 ∧ 𝐴 ⊆ 𝐵 ∧ Ord 𝐵) → Ord 𝐴)

Syntax hints:   → wi 4   ∧ wa 400   ∧ w3a 1101   ⊆ wss 3907  Tr wtr 5212   E cep 5551   We wwe 5604  Ord word 6349

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1818  ax-4 1832  ax-5 1933

This theorem depends on definitions:  df-bi 210  df-an 401  df-3an 1103  df-ral 3080  df-ss 3924  df-po 5560  df-so 5561  df-fr 5605  df-we 5607  df-ord 6353

This theorem is referenced by:  ordin  6380  ssorduni  7766  ordsuci  7795  ordom  7860  ordtypelem2  9469  hartogs  9494  card2on  9504  tskwe  9924  ondomon  10535  dford3lem2  43616  dford3  43617  iunord  50305