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Theorem dfiota2 5220
 Description: Alternate definition for descriptions. Definition 8.18 in [Quine] p. 56. (Contributed by Andrew Salmon, 30-Jun-2011.)
Assertion
Ref Expression
dfiota2
Distinct variable groups:   ,   ,
Allowed substitution hint:   ()

Proof of Theorem dfiota2
StepHypRef Expression
1 df-iota 5219 . 2
2 df-sn 3646 . . . . . 6
32eqeq2i 2293 . . . . 5
4 abbi 2393 . . . . 5
53, 4bitr4i 243 . . . 4
65abbii 2395 . . 3
76unieqi 3837 . 2
81, 7eqtri 2303 1
 Colors of variables: wff set class Syntax hints:   wb 176  wal 1527   wceq 1623  cab 2269  csn 3640  cuni 3827  cio 5217 This theorem is referenced by:  nfiota1  5221  nfiotad  5222  cbviota  5224  sb8iota  5226  iotaval  5230  iotanul  5234  fv2  5520 This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8  ax-gen 1533  ax-5 1544  ax-17 1603  ax-9 1635  ax-8 1643  ax-6 1703  ax-7 1708  ax-11 1715  ax-12 1866  ax-ext 2264 This theorem depends on definitions:  df-bi 177  df-or 359  df-an 360  df-tru 1310  df-ex 1529  df-nf 1532  df-sb 1630  df-clab 2270  df-cleq 2276  df-clel 2279  df-nfc 2408  df-rex 2549  df-sn 3646  df-uni 3828  df-iota 5219
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