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Theorem unabs 3601
Description: Absorption law for union. (Contributed by NM, 16-Apr-2006.)
Assertion
Ref Expression
unabs  |-  ( A  u.  ( A  i^i  B ) )  =  A

Proof of Theorem unabs
StepHypRef Expression
1 inss1 3591 . 2  |-  ( A  i^i  B )  C_  A
2 ssequn2 3550 . 2  |-  ( ( A  i^i  B ) 
C_  A  <->  ( A  u.  ( A  i^i  B
) )  =  A )
31, 2mpbi 208 1  |-  ( A  u.  ( A  i^i  B ) )  =  A
Colors of variables: wff setvar class
Syntax hints:    = wceq 1369    u. cun 3347    i^i cin 3348    C_ wss 3349
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1591  ax-4 1602  ax-5 1670  ax-6 1708  ax-7 1728  ax-10 1775  ax-11 1780  ax-12 1792  ax-13 1943  ax-ext 2423
This theorem depends on definitions:  df-bi 185  df-or 370  df-an 371  df-tru 1372  df-ex 1587  df-nf 1590  df-sb 1701  df-clab 2430  df-cleq 2436  df-clel 2439  df-nfc 2577  df-v 2995  df-un 3354  df-in 3356  df-ss 3363
This theorem is referenced by:  volun  21048
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