Theorem sssucid 4541

Description: A class is included in its own successor. Part of Proposition 7.23 of [TakeutiZaring] p. 41 (generalized to arbitrary classes). (Contributed by NM, 31-May-1994.)

Assertion

Ref	Expression
sssucid	|- A C_ suc A

Proof of Theorem sssucid

Step	Hyp	Ref	Expression
1		ssun1 3386	. 2 |- A C_ ( A u. { A } )
2		df-suc 4497	. 2 |- suc A = ( A u. { A } )
3	1, 2	sseqtrri 3277	1 |- A C_ suc A

Syntax hints:   u. cun 3212   C_ wss 3214   {csn 3694   suc csuc 4491

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-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 2216

This theorem depends on definitions:  df-bi 117  df-tru 1401  df-nf 1510  df-sb 1812  df-clab 2221  df-cleq 2227  df-clel 2230  df-nfc 2375  df-v 2817  df-un 3218  df-in 3220  df-ss 3227  df-suc 4497

This theorem is referenced by:  trsuc  4548  ordsuc  4690  0elnn  4746  sucinc  6691  sucinc2  6692  oasuc  6710  phplem4  7122  phplem4dom  7129  phplem4on  7135  fiintim  7204  fidcenumlemrk  7237  fidcenumlemr  7238  bj-nntrans  16847