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Theorem ssiun2 3728
 Description: Identity law for subset of an indexed union. (Contributed by NM, 12-Oct-2003.) (Proof shortened by Andrew Salmon, 25-Jul-2011.)
Assertion
Ref Expression
ssiun2

Proof of Theorem ssiun2
Dummy variable is distinct from all other variables.
StepHypRef Expression
1 rspe 2387 . . . 4
21ex 112 . . 3
3 eliun 3689 . . 3
42, 3syl6ibr 155 . 2
54ssrdv 2979 1
 Colors of variables: wff set class Syntax hints:   wi 4   wcel 1409  wrex 2324   wss 2945  ciun 3685 This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 103  ax-ia2 104  ax-ia3 105  ax-io 640  ax-5 1352  ax-7 1353  ax-gen 1354  ax-ie1 1398  ax-ie2 1399  ax-8 1411  ax-10 1412  ax-11 1413  ax-i12 1414  ax-bndl 1415  ax-4 1416  ax-17 1435  ax-i9 1439  ax-ial 1443  ax-i5r 1444  ax-ext 2038 This theorem depends on definitions:  df-bi 114  df-tru 1262  df-nf 1366  df-sb 1662  df-clab 2043  df-cleq 2049  df-clel 2052  df-nfc 2183  df-ral 2328  df-rex 2329  df-v 2576  df-in 2952  df-ss 2959  df-iun 3687 This theorem is referenced by:  ssiun2s  3729  triun  3895
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