Theorem tpid2 3706

Description: One of the three elements of an unordered triple. (Contributed by NM, 7-Apr-1994.) (Proof shortened by Andrew Salmon, 29-Jun-2011.)

Hypothesis

Ref	Expression
tpid2.1	|- B e. _V

Assertion

Ref	Expression
tpid2	|- B e. { A , B , C }

Proof of Theorem tpid2

Step	Hyp	Ref	Expression
1		eqid 2177	. . 3 |- B = B
2	1	3mix2i 1170	. 2 |- ( B = A \/ B = B \/ B = C )
3		tpid2.1	. . 3 |- B e. _V
4	3	eltp 3641	. 2 |- ( B e. { A , B , C } <-> ( B = A \/ B = B \/ B = C ) )
5	2, 4	mpbir 146	1 |- B e. { A , B , C }

Syntax hints:   \/ w3o 977   = wceq 1353   e. wcel 2148   _Vcvv 2738   {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-3or 979  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-sn 3599  df-pr 3600  df-tp 3601

This theorem is referenced by: (None)