Theorem ordgt0ge1 6668

Description: Two ways to express that an ordinal class is positive. (Contributed by NM, 21-Dec-2004.)

Assertion

Ref	Expression
ordgt0ge1	|- ( Ord A -> ( (/) e. A <-> 1o C_ A ) )

Proof of Theorem ordgt0ge1

Step	Hyp	Ref	Expression
1		0elon 4513	. . 3 |- (/) e. On
2		ordelsuc 4627	. . 3 |- ( ( (/) e. On /\ Ord A ) -> ( (/) e. A <-> suc (/) C_ A ) )
3	1, 2	mpan 424	. 2 |- ( Ord A -> ( (/) e. A <-> suc (/) C_ A ) )
4		df-1o 6647	. . 3 |- 1o = suc (/)
5	4	sseq1i 3264	. 2 |- ( 1o C_ A <-> suc (/) C_ A )
6	3, 5	bitr4di 198	1 |- ( Ord A -> ( (/) e. A <-> 1o C_ A ) )

Syntax hints:   -> wi 4   <-> wb 105   e. wcel 2203   C_ wss 3211   (/)c0 3508   Ord word 4483   Oncon0 4484   suc csuc 4486   1oc1o 6640

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 619  ax-in2 620  ax-io 717  ax-5 1496  ax-7 1497  ax-gen 1498  ax-ie1 1542  ax-ie2 1543  ax-8 1553  ax-10 1554  ax-11 1555  ax-i12 1556  ax-bndl 1558  ax-4 1559  ax-17 1575  ax-i9 1579  ax-ial 1583  ax-i5r 1584  ax-ext 2214  ax-nul 4236

This theorem depends on definitions:  df-bi 117  df-tru 1401  df-nf 1510  df-sb 1812  df-clab 2219  df-cleq 2225  df-clel 2228  df-nfc 2373  df-ral 2525  df-rex 2526  df-v 2815  df-dif 3213  df-un 3215  df-in 3217  df-ss 3224  df-nul 3509  df-pw 3671  df-sn 3695  df-uni 3915  df-tr 4209  df-iord 4487  df-on 4489  df-suc 4492  df-1o 6647

This theorem is referenced by:  ordge1n0im  6669  archnqq  7732