Theorem 0lt1o 6594

Description: Ordinal zero is less than ordinal one. (Contributed by NM, 5-Jan-2005.)

Assertion

Ref	Expression
0lt1o	⊢ ∅ ∈ 1o

Proof of Theorem 0lt1o

Step	Hyp	Ref	Expression
1		eqid 2229	. 2 ⊢ ∅ = ∅
2		el1o 6591	. 2 ⊢ (∅ ∈ 1o ↔ ∅ = ∅)
3	1, 2	mpbir 146	1 ⊢ ∅ ∈ 1o

Syntax hints:   = wceq 1395   ∈ wcel 2200  ∅c0 3491  1_oc1o 6561

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-in1 617  ax-in2 618  ax-io 714  ax-5 1493  ax-7 1494  ax-gen 1495  ax-ie1 1539  ax-ie2 1540  ax-8 1550  ax-10 1551  ax-11 1552  ax-i12 1553  ax-bndl 1555  ax-4 1556  ax-17 1572  ax-i9 1576  ax-ial 1580  ax-i5r 1581  ax-ext 2211  ax-nul 4210

This theorem depends on definitions:  df-bi 117  df-tru 1398  df-nf 1507  df-sb 1809  df-clab 2216  df-cleq 2222  df-clel 2225  df-nfc 2361  df-v 2801  df-dif 3199  df-un 3201  df-nul 3492  df-sn 3672  df-suc 4462  df-1o 6568

This theorem is referenced by:  nnaordex  6682  1domsn  6984  dom1o  6985  snexxph  7128  difinfsnlem  7277  difinfsn  7278  0ct  7285  ctmlemr  7286  ctssdclemn0  7288  exmidfodomrlemr  7391  exmidfodomrlemrALT  7392  iftrueb01  7419  1lt2pi  7538  archnqq  7615  prarloclemarch2  7617  pwle2  16423