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Theorem ss2ab 3411
 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 2574 . . 3
2 nfab1 2574 . . 3
31, 2dfss2f 3339 . 2
4 abid 2424 . . . 4
5 abid 2424 . . . 4
64, 5imbi12i 317 . . 3
76albii 1575 . 2
83, 7bitri 241 1
 Colors of variables: wff set class Syntax hints:   wi 4   wb 177  wal 1549   wcel 1725  cab 2422   wss 3320 This theorem is referenced by:  abss  3412  ssab  3413  ss2abi  3415  ss2abdv  3416  ss2rab  3419  rabss2  3426 This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8  ax-gen 1555  ax-5 1566  ax-17 1626  ax-9 1666  ax-8 1687  ax-6 1744  ax-7 1749  ax-11 1761  ax-12 1950  ax-ext 2417 This theorem depends on definitions:  df-bi 178  df-or 360  df-an 361  df-tru 1328  df-ex 1551  df-nf 1554  df-sb 1659  df-clab 2423  df-cleq 2429  df-clel 2432  df-nfc 2561  df-in 3327  df-ss 3334
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