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Theorem undifabs 3905
 Description: Absorption of difference by union. (Contributed by NM, 18-Aug-2013.)
Assertion
Ref Expression
undifabs

Proof of Theorem undifabs
StepHypRef Expression
1 undif3 3758 . 2
2 unidm 3646 . . 3
32difeq1i 3617 . 2
4 difdif 3629 . 2
51, 3, 43eqtri 2490 1
 Colors of variables: wff setvar class Syntax hints:  =wceq 1395  \cdif 3472  u.cun 3473 This theorem is referenced by:  dfif5  3957 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1618  ax-4 1631  ax-5 1704  ax-6 1747  ax-7 1790  ax-10 1837  ax-11 1842  ax-12 1854  ax-13 1999  ax-ext 2435 This theorem depends on definitions:  df-bi 185  df-or 370  df-an 371  df-tru 1398  df-ex 1613  df-nf 1617  df-sb 1740  df-clab 2443  df-cleq 2449  df-clel 2452  df-nfc 2607  df-rab 2816  df-v 3111  df-dif 3478  df-un 3480
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