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Theorem snsstp3 3672
 Description: A singleton is a subset of an unordered triple containing its member. (Contributed by NM, 9-Oct-2013.)
Assertion
Ref Expression
snsstp3 {𝐶} ⊆ {𝐴, 𝐵, 𝐶}

Proof of Theorem snsstp3
StepHypRef Expression
1 ssun2 3240 . 2 {𝐶} ⊆ ({𝐴, 𝐵} ∪ {𝐶})
2 df-tp 3535 . 2 {𝐴, 𝐵, 𝐶} = ({𝐴, 𝐵} ∪ {𝐶})
31, 2sseqtrri 3132 1 {𝐶} ⊆ {𝐴, 𝐵, 𝐶}
 Colors of variables: wff set class Syntax hints:   ∪ cun 3069   ⊆ wss 3071  {csn 3527  {cpr 3528  {ctp 3529 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 698  ax-5 1423  ax-7 1424  ax-gen 1425  ax-ie1 1469  ax-ie2 1470  ax-8 1482  ax-10 1483  ax-11 1484  ax-i12 1485  ax-bndl 1486  ax-4 1487  ax-17 1506  ax-i9 1510  ax-ial 1514  ax-i5r 1515  ax-ext 2121 This theorem depends on definitions:  df-bi 116  df-tru 1334  df-nf 1437  df-sb 1736  df-clab 2126  df-cleq 2132  df-clel 2135  df-nfc 2270  df-v 2688  df-un 3075  df-in 3077  df-ss 3084  df-tp 3535 This theorem is referenced by:  sstpr  3684
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