Theorem unundir 3426

Description: Union distributes over itself. (Contributed by NM, 17-Aug-2004.)

Assertion

Ref	Expression
unundir	|- ((A u. B) u. C) = ((A u. C) u. (B u. C))

Proof of Theorem unundir

Step	Hyp	Ref	Expression
1		unidm 3408	. . 3 |- (C u. C) = C
2	1	uneq2i 3416	. 2 |- ((A u. B) u. (C u. C)) = ((A u. B) u. C)
3		un4 3424	. 2 |- ((A u. B) u. (C u. C)) = ((A u. C) u. (B u. C))
4	2, 3	eqtr3i 2375	1 |- ((A u. B) u. C) = ((A u. C) u. (B u. C))

Syntax hints:   = wceq 1642   u. cun 3208

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1546  ax-5 1557  ax-17 1616  ax-9 1654  ax-8 1675  ax-6 1729  ax-7 1734  ax-11 1746  ax-12 1925  ax-ext 2334

This theorem depends on definitions:  df-bi 177  df-or 359  df-an 360  df-nan 1288  df-tru 1319  df-ex 1542  df-nf 1545  df-sb 1649  df-clab 2340  df-cleq 2346  df-clel 2349  df-nfc 2479  df-v 2862  df-nin 3212  df-compl 3213  df-un 3215

This theorem is referenced by: (None)