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Theorem ss2ab 3567
Description: Class abstractions in a subclass relationship. (Contributed by NM, 3-Jul-1994.)
Assertion
Ref Expression
ss2ab

Proof of Theorem ss2ab
StepHypRef Expression
1 nfab1 2621 . . 3
2 nfab1 2621 . . 3
31, 2dfss2f 3494 . 2
4 abid 2444 . . . 4
5 abid 2444 . . . 4
64, 5imbi12i 326 . . 3
76albii 1640 . 2
83, 7bitri 249 1
Colors of variables: wff setvar class
Syntax hints:  ->wi 4  <->wb 184  A.wal 1393  e.wcel 1818  {cab 2442  C_wss 3475
This theorem is referenced by:  abss  3568  ssab  3569  ss2abi  3571  ss2abdv  3572  ss2rab  3575  rabss2  3582  rabsssn  32920
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-in 3482  df-ss 3489
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