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Theorem tpssi 3760
Description: A triple of elements of a class is a subset of the class. (Contributed by Alexander van der Vekens, 1-Feb-2018.)
Assertion
Ref Expression
tpssi  |-  ( ( A  e.  D  /\  B  e.  D  /\  C  e.  D )  ->  { A ,  B ,  C }  C_  D
)

Proof of Theorem tpssi
StepHypRef Expression
1 df-tp 3601 . 2  |-  { A ,  B ,  C }  =  ( { A ,  B }  u.  { C } )
2 prssi 3751 . . . 4  |-  ( ( A  e.  D  /\  B  e.  D )  ->  { A ,  B }  C_  D )
323adant3 1017 . . 3  |-  ( ( A  e.  D  /\  B  e.  D  /\  C  e.  D )  ->  { A ,  B }  C_  D )
4 snssi 3737 . . . 4  |-  ( C  e.  D  ->  { C }  C_  D )
543ad2ant3 1020 . . 3  |-  ( ( A  e.  D  /\  B  e.  D  /\  C  e.  D )  ->  { C }  C_  D )
63, 5unssd 3312 . 2  |-  ( ( A  e.  D  /\  B  e.  D  /\  C  e.  D )  ->  ( { A ,  B }  u.  { C } )  C_  D
)
71, 6eqsstrid 3202 1  |-  ( ( A  e.  D  /\  B  e.  D  /\  C  e.  D )  ->  { A ,  B ,  C }  C_  D
)
Colors of variables: wff set class
Syntax hints:    -> wi 4    /\ w3a 978    e. wcel 2148    u. cun 3128    C_ wss 3130   {csn 3593   {cpr 3594   {ctp 3595
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 709  ax-5 1447  ax-7 1448  ax-gen 1449  ax-ie1 1493  ax-ie2 1494  ax-8 1504  ax-10 1505  ax-11 1506  ax-i12 1507  ax-bndl 1509  ax-4 1510  ax-17 1526  ax-i9 1530  ax-ial 1534  ax-i5r 1535  ax-ext 2159
This theorem depends on definitions:  df-bi 117  df-3an 980  df-tru 1356  df-nf 1461  df-sb 1763  df-clab 2164  df-cleq 2170  df-clel 2173  df-nfc 2308  df-v 2740  df-un 3134  df-in 3136  df-ss 3143  df-sn 3599  df-pr 3600  df-tp 3601
This theorem is referenced by: (None)
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