Theorem tpidm12 3770

Description: Unordered triple { A , A , B } is just an overlong way to write { A , B }. (Contributed by David A. Wheeler, 10-May-2015.)

Assertion

Ref	Expression
tpidm12	|- { A , A , B } = { A , B }

Proof of Theorem tpidm12

Step	Hyp	Ref	Expression
1		dfsn2 3683	. . 3 |- { A } = { A , A }
2	1	uneq1i 3357	. 2 |- ( { A } u. { B } ) = ( { A , A } u. { B } )
3		df-pr 3676	. 2 |- { A , B } = ( { A } u. { B } )
4		df-tp 3677	. 2 |- { A , A , B } = ( { A , A } u. { B } )
5	2, 3, 4	3eqtr4ri 2263	1 |- { A , A , B } = { A , B }

Syntax hints:   = wceq 1397   u. cun 3198   {csn 3669   {cpr 3670   {ctp 3671

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 716  ax-5 1495  ax-7 1496  ax-gen 1497  ax-ie1 1541  ax-ie2 1542  ax-8 1552  ax-10 1553  ax-11 1554  ax-i12 1555  ax-bndl 1557  ax-4 1558  ax-17 1574  ax-i9 1578  ax-ial 1582  ax-i5r 1583  ax-ext 2213

This theorem depends on definitions:  df-bi 117  df-tru 1400  df-nf 1509  df-sb 1811  df-clab 2218  df-cleq 2224  df-clel 2227  df-nfc 2363  df-v 2804  df-un 3204  df-pr 3676  df-tp 3677

This theorem is referenced by:  tpidm13  3771  tpidm23  3772  tpidm  3773