Theorem prid1g 3680

Description: An unordered pair contains its first member. Part of Theorem 7.6 of [Quine] p. 49. (Contributed by Stefan Allan, 8-Nov-2008.)

Assertion

Ref	Expression
prid1g	|- ( A e. V -> A e. { A , B } )

Proof of Theorem prid1g

Step	Hyp	Ref	Expression
1		eqid 2165	. . 3 |- A = A
2	1	orci 721	. 2 |- ( A = A \/ A = B )
3		elprg 3596	. 2 |- ( A e. V -> ( A e. { A , B } <-> ( A = A \/ A = B ) ) )
4	2, 3	mpbiri 167	1 |- ( A e. V -> A e. { A , B } )

Syntax hints:   -> wi 4   \/ wo 698   = wceq 1343   e. wcel 2136   {cpr 3577

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 1435  ax-7 1436  ax-gen 1437  ax-ie1 1481  ax-ie2 1482  ax-8 1492  ax-10 1493  ax-11 1494  ax-i12 1495  ax-bndl 1497  ax-4 1498  ax-17 1514  ax-i9 1518  ax-ial 1522  ax-i5r 1523  ax-ext 2147

This theorem depends on definitions:  df-bi 116  df-tru 1346  df-nf 1449  df-sb 1751  df-clab 2152  df-cleq 2158  df-clel 2161  df-nfc 2297  df-v 2728  df-un 3120  df-sn 3582  df-pr 3583

This theorem is referenced by:  prid2g  3681  prid1  3682  preqr1g  3746  opth1  4214  en2lp  4531  acexmidlemcase  5837  en2eqpr  6873  m1expcl2  10477  maxabslemval  11150  xrmaxiflemval  11191  xrmaxaddlem  11201  2strbasg  12496  2strbas1g  12499  coseq0negpitopi  13397