Theorem snss 3753

Description: The singleton of an element of a class is a subset of the class (inference form of snssg 3752). Theorem 7.4 of [Quine] p. 49. (Contributed by NM, 21-Jun-1993.) (Proof shortened by BJ, 1-Jan-2025.)

Hypothesis

Ref	Expression
snss.1	|- A e. _V

Assertion

Ref	Expression
snss	|- ( A e. B <-> { A } C_ B )

Proof of Theorem snss

Step	Hyp	Ref	Expression
1		snss.1	. 2 |- A e. _V
2		snssg 3752	. 2 |- ( A e. _V -> ( A e. B <-> { A } C_ B ) )
3	1, 2	ax-mp 5	1 |- ( A e. B <-> { A } C_ B )

Syntax hints:   <-> wb 105   e. wcel 2164   _Vcvv 2760   C_ wss 3153   {csn 3618

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 710  ax-5 1458  ax-7 1459  ax-gen 1460  ax-ie1 1504  ax-ie2 1505  ax-8 1515  ax-10 1516  ax-11 1517  ax-i12 1518  ax-bndl 1520  ax-4 1521  ax-17 1537  ax-i9 1541  ax-ial 1545  ax-i5r 1546  ax-ext 2175

This theorem depends on definitions:  df-bi 117  df-tru 1367  df-nf 1472  df-sb 1774  df-clab 2180  df-cleq 2186  df-clel 2189  df-nfc 2325  df-v 2762  df-in 3159  df-ss 3166  df-sn 3624

This theorem is referenced by:  snssgOLD  3754  prss  3774  tpss  3784  snelpw  4242  sspwb  4245  mss  4255  exss  4256  reg2exmidlema  4566  elomssom  4637  relsn  4764  fnressn  5744  un0mulcl  9274  nn0ssz  9335  fimaxre2  11370  fsum2dlemstep  11577  fsumabs  11608  fsumiun  11620  fprod2dlemstep  11765  elply2  14881  elplyd  14887  ply1term  14889  plymullem  14896  bdsnss  15365