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Theorem snel1c 4140
Description: A singleton is an element of cardinal one. (Contributed by SF, 13-Jan-2015.)
Hypothesis
Ref Expression
snel1c.1 A V
Assertion
Ref Expression
snel1c {A} 1c

Proof of Theorem snel1c
Dummy variable x is distinct from all other variables.
StepHypRef Expression
1 eqid 2353 . . 3 {A} = {A}
2 snel1c.1 . . . 4 A V
3 sneq 3744 . . . . 5 (x = A → {x} = {A})
43eqeq2d 2364 . . . 4 (x = A → ({A} = {x} ↔ {A} = {A}))
52, 4spcev 2946 . . 3 ({A} = {A} → x{A} = {x})
61, 5ax-mp 5 . 2 x{A} = {x}
7 el1c 4139 . 2 ({A} 1cx{A} = {x})
86, 7mpbir 200 1 {A} 1c
Colors of variables: wff setvar class
Syntax hints:  wex 1541   = wceq 1642   wcel 1710  Vcvv 2859  {csn 3737  1cc1c 4134
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1546  ax-5 1557  ax-17 1616  ax-9 1654  ax-8 1675  ax-6 1729  ax-7 1734  ax-11 1746  ax-12 1925  ax-ext 2334  ax-nin 4078  ax-sn 4087
This theorem depends on definitions:  df-bi 177  df-or 359  df-an 360  df-nan 1288  df-tru 1319  df-ex 1542  df-nf 1545  df-sb 1649  df-clab 2340  df-cleq 2346  df-clel 2349  df-nfc 2478  df-ne 2518  df-v 2861  df-nin 3211  df-compl 3212  df-in 3213  df-un 3214  df-dif 3215  df-ss 3259  df-nul 3551  df-sn 3741  df-1c 4136
This theorem is referenced by:  snel1cg  4141  sikss1c1c  4267  ins2kss  4279  ins3kss  4280  sikexg  4296  ins2kexg  4305  ins3kexg  4306  tfin1c  4499  nnpweq  4523  sfin01  4528  pw1fnval  5851  brpw1fn  5854  df1c3  6140  tc1c  6165  ce0nn  6180  nc0le1  6216  brtcfn  6246
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