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Theorem unss2 3674
 Description: Subclass law for union of classes. Exercise 7 of [TakeutiZaring] p. 18. (Contributed by NM, 14-Oct-1999.)
Assertion
Ref Expression
unss2

Proof of Theorem unss2
StepHypRef Expression
1 unss1 3672 . 2
2 uncom 3647 . 2
3 uncom 3647 . 2
41, 2, 33sstr4g 3544 1
 Colors of variables: wff setvar class Syntax hints:  ->wi 4  u.cun 3473  C_wss 3475 This theorem is referenced by:  unss12  3675  ord3ex  4642  xpider  7401  fin1a2lem13  8813  canthp1lem2  9052  uniioombllem3  21994  volcn  22015  dvres2lem  22314  bnj1413  34091  bnj1408  34092 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-v 3111  df-un 3480  df-in 3482  df-ss 3489
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