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Theorem rext 4639
 Description: A theorem similar to extensionality, requiring the existence of a singleton. Exercise 8 of [TakeutiZaring] p. 16. (Contributed by NM, 10-Aug-1993.)
Assertion
Ref Expression
rext
Distinct variable group:   ,,

Proof of Theorem rext
StepHypRef Expression
1 ssnid 4001 . . 3
2 snex 4632 . . . 4
3 eleq2 2475 . . . . 5
4 eleq2 2475 . . . . 5
53, 4imbi12d 318 . . . 4
62, 5spcv 3150 . . 3
71, 6mpi 20 . 2
8 elsn 3986 . . 3
9 equcomi 1817 . . 3
108, 9sylbi 195 . 2
117, 10syl 17 1
 Colors of variables: wff setvar class Syntax hints:   wi 4  wal 1403   wceq 1405   wcel 1842  csn 3972 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1639  ax-4 1652  ax-5 1725  ax-6 1771  ax-7 1814  ax-9 1846  ax-10 1861  ax-11 1866  ax-12 1878  ax-13 2026  ax-ext 2380  ax-sep 4517  ax-nul 4525  ax-pr 4630 This theorem depends on definitions:  df-bi 185  df-or 368  df-an 369  df-tru 1408  df-ex 1634  df-nf 1638  df-sb 1764  df-clab 2388  df-cleq 2394  df-clel 2397  df-nfc 2552  df-ne 2600  df-v 3061  df-dif 3417  df-un 3419  df-nul 3739  df-sn 3973  df-pr 3975 This theorem is referenced by: (None)
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