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Theorem iunconst 3913
Description: Indexed union of a constant class, i.e. where  B does not depend on  x. (Contributed by NM, 5-Sep-2004.) (Proof shortened by Andrew Salmon, 25-Jul-2011.)
Assertion
Ref Expression
iunconst  |-  ( A  =/=  (/)  ->  U_ x  e.  A  B  =  B )
Distinct variable groups:    x, A    x, B

Proof of Theorem iunconst
Dummy variable  y is distinct from all other variables.
StepHypRef Expression
1 r19.9rzv 3548 . . 3  |-  ( A  =/=  (/)  ->  ( y  e.  B  <->  E. x  e.  A  y  e.  B )
)
2 eliun 3909 . . 3  |-  ( y  e.  U_ x  e.  A  B  <->  E. x  e.  A  y  e.  B )
31, 2syl6rbbr 255 . 2  |-  ( A  =/=  (/)  ->  ( y  e.  U_ x  e.  A  B 
<->  y  e.  B ) )
43eqrdv 2281 1  |-  ( A  =/=  (/)  ->  U_ x  e.  A  B  =  B )
Colors of variables: wff set class
Syntax hints:    -> wi 4    = wceq 1623    e. wcel 1684    =/= wne 2446   E.wrex 2544   (/)c0 3455   U_ciun 3905
This theorem is referenced by:  iununi  3986  abianfplem  6470  oe1m  6543  oarec  6560  oelim2  6593  imfstnrelc  25081  bnj1143  28822
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-ne 2448  df-ral 2548  df-rex 2549  df-v 2790  df-dif 3155  df-nul 3456  df-iun 3907
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