Theorem tpid2 3668

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 2154	. . 3 |- B = B
2	1	3mix2i 1155	. 2 |- ( B = A \/ B = B \/ B = C )
3		tpid2.1	. . 3 |- B e. _V
4	3	eltp 3603	. 2 |- ( B e. { A , B , C } <-> ( B = A \/ B = B \/ B = C ) )
5	2, 4	mpbir 145	1 |- B e. { A , B , C }

Syntax hints:   \/ w3o 962   = wceq 1332   e. wcel 2125   _Vcvv 2709   {ctp 3558

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 699  ax-5 1424  ax-7 1425  ax-gen 1426  ax-ie1 1470  ax-ie2 1471  ax-8 1481  ax-10 1482  ax-11 1483  ax-i12 1484  ax-bndl 1486  ax-4 1487  ax-17 1503  ax-i9 1507  ax-ial 1511  ax-i5r 1512  ax-ext 2136

This theorem depends on definitions:  df-bi 116  df-3or 964  df-tru 1335  df-nf 1438  df-sb 1740  df-clab 2141  df-cleq 2147  df-clel 2150  df-nfc 2285  df-v 2711  df-un 3102  df-sn 3562  df-pr 3563  df-tp 3564

This theorem is referenced by: (None)