Theorem dif20el 7585

Description: An ordinal greater than one is greater than zero. (Contributed by Mario Carneiro, 25-May-2015.)

Assertion

Ref	Expression
dif20el	|- ( A e. ( On \ 2o ) -> (/) e. A )

Proof of Theorem dif20el

Step	Hyp	Ref	Expression
1		ondif2 7582	. . 3 |- ( A e. ( On \ 2o ) <-> ( A e. On /\ 1o e. A ) )
2	1	simprbi 480	. 2 |- ( A e. ( On \ 2o ) -> 1o e. A )
3		0lt1o 7584	. . 3 |- (/) e. 1o
4		eldifi 3732	. . . 4 |- ( A e. ( On \ 2o ) -> A e. On )
5		ontr1 5771	. . . 4 |- ( A e. On -> ( ( (/) e. 1o /\ 1o e. A ) -> (/) e. A ) )
6	4, 5	syl 17	. . 3 |- ( A e. ( On \ 2o ) -> ( ( (/) e. 1o /\ 1o e. A ) -> (/) e. A ) )
7	3, 6	mpani 712	. 2 |- ( A e. ( On \ 2o ) -> ( 1o e. A -> (/) e. A ) )
8	2, 7	mpd 15	1 |- ( A e. ( On \ 2o ) -> (/) e. A )

Syntax hints:   -> wi 4   /\ wa 384   e. wcel 1990   \ cdif 3571   (/)c0 3915   Oncon0 5723   1oc1o 7553   2oc2o 7554

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-8 1992  ax-9 1999  ax-10 2019  ax-11 2034  ax-12 2047  ax-13 2246  ax-ext 2602  ax-sep 4781  ax-nul 4789  ax-pr 4906  ax-un 6949

This theorem depends on definitions:  df-bi 197  df-or 385  df-an 386  df-3or 1038  df-3an 1039  df-tru 1486  df-ex 1705  df-nf 1710  df-sb 1881  df-eu 2474  df-mo 2475  df-clab 2609  df-cleq 2615  df-clel 2618  df-nfc 2753  df-ne 2795  df-ral 2917  df-rex 2918  df-rab 2921  df-v 3202  df-sbc 3436  df-dif 3577  df-un 3579  df-in 3581  df-ss 3588  df-pss 3590  df-nul 3916  df-if 4087  df-pw 4160  df-sn 4178  df-pr 4180  df-tp 4182  df-op 4184  df-uni 4437  df-br 4654  df-opab 4713  df-tr 4753  df-eprel 5029  df-po 5035  df-so 5036  df-fr 5073  df-we 5075  df-ord 5726  df-on 5727  df-suc 5729  df-1o 7560  df-2o 7561

This theorem is referenced by:  oeordi  7667  oeworde  7673  oelimcl  7680  oeeulem  7681  oeeui  7682