Theorem sssucid 4400

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 3290	. 2 |- A C_ ( A u. { A } )
2		df-suc 4356	. 2 |- suc A = ( A u. { A } )
3	1, 2	sseqtrri 3182	1 |- A C_ suc A

Syntax hints:   u. cun 3119   C_ wss 3121   {csn 3583   suc csuc 4350

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-io 704  ax-5 1440  ax-7 1441  ax-gen 1442  ax-ie1 1486  ax-ie2 1487  ax-8 1497  ax-10 1498  ax-11 1499  ax-i12 1500  ax-bndl 1502  ax-4 1503  ax-17 1519  ax-i9 1523  ax-ial 1527  ax-i5r 1528  ax-ext 2152

This theorem depends on definitions:  df-bi 116  df-tru 1351  df-nf 1454  df-sb 1756  df-clab 2157  df-cleq 2163  df-clel 2166  df-nfc 2301  df-v 2732  df-un 3125  df-in 3127  df-ss 3134  df-suc 4356

This theorem is referenced by:  trsuc  4407  ordsuc  4547  0elnn  4603  sucinc  6424  sucinc2  6425  oasuc  6443  phplem4  6833  phplem4dom  6840  phplem4on  6845  fiintim  6906  fidcenumlemrk  6931  fidcenumlemr  6932  bj-nntrans  13986