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Theorem ss2iun 4183
Description: Subclass theorem for indexed union. (Contributed by NM, 26-Nov-2003.) (Proof shortened by Andrew Salmon, 25-Jul-2011.)
Assertion
Ref Expression
ss2iun  |-  ( A. x  e.  A  B  C_  C  ->  U_ x  e.  A  B  C_  U_ x  e.  A  C )

Proof of Theorem ss2iun
Dummy variable  y is distinct from all other variables.
StepHypRef Expression
1 ssel 3347 . . . . 5  |-  ( B 
C_  C  ->  (
y  e.  B  -> 
y  e.  C ) )
21ralimi 2789 . . . 4  |-  ( A. x  e.  A  B  C_  C  ->  A. x  e.  A  ( y  e.  B  ->  y  e.  C ) )
3 rexim 2818 . . . 4  |-  ( A. x  e.  A  (
y  e.  B  -> 
y  e.  C )  ->  ( E. x  e.  A  y  e.  B  ->  E. x  e.  A  y  e.  C )
)
42, 3syl 16 . . 3  |-  ( A. x  e.  A  B  C_  C  ->  ( E. x  e.  A  y  e.  B  ->  E. x  e.  A  y  e.  C ) )
5 eliun 4172 . . 3  |-  ( y  e.  U_ x  e.  A  B  <->  E. x  e.  A  y  e.  B )
6 eliun 4172 . . 3  |-  ( y  e.  U_ x  e.  A  C  <->  E. x  e.  A  y  e.  C )
74, 5, 63imtr4g 270 . 2  |-  ( A. x  e.  A  B  C_  C  ->  ( y  e.  U_ x  e.  A  B  ->  y  e.  U_ x  e.  A  C
) )
87ssrdv 3359 1  |-  ( A. x  e.  A  B  C_  C  ->  U_ x  e.  A  B  C_  U_ x  e.  A  C )
Colors of variables: wff setvar class
Syntax hints:    -> wi 4    e. wcel 1761   A.wral 2713   E.wrex 2714    C_ wss 3325   U_ciun 4168
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1596  ax-4 1607  ax-5 1675  ax-6 1713  ax-7 1733  ax-10 1780  ax-11 1785  ax-12 1797  ax-13 1948  ax-ext 2422
This theorem depends on definitions:  df-bi 185  df-or 370  df-an 371  df-tru 1367  df-ex 1592  df-nf 1595  df-sb 1706  df-clab 2428  df-cleq 2434  df-clel 2437  df-nfc 2566  df-ral 2718  df-rex 2719  df-v 2972  df-in 3332  df-ss 3339  df-iun 4170
This theorem is referenced by:  iuneq2  4184  oawordri  6985  omwordri  7007  oewordri  7027  oeworde  7028  r1val1  7989  cfslb2n  8433  imasaddvallem  14463  dprdss  16516  tgcmp  18904  txcmplem1  19114  txcmplem2  19115  xkococnlem  19132  alexsubALT  19523  ptcmplem3  19526  metnrmlem2  20336  uniiccvol  20960  dvfval  21272  filnetlem3  28510  sstotbnd2  28582  equivtotbnd  28586  bnj1145  31801  bnj1136  31805
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