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Theorem unssd 3116
Description: A deduction showing the union of two subclasses is a subclass. (Contributed by Jonathan Ben-Naim, 3-Jun-2011.)
Hypotheses
Ref Expression
unssd.1  |-  ( ph  ->  A  C_  C )
unssd.2  |-  ( ph  ->  B  C_  C )
Assertion
Ref Expression
unssd  |-  ( ph  ->  ( A  u.  B
)  C_  C )

Proof of Theorem unssd
StepHypRef Expression
1 unssd.1 . 2  |-  ( ph  ->  A  C_  C )
2 unssd.2 . 2  |-  ( ph  ->  B  C_  C )
3 unss 3114 . . 3  |-  ( ( A  C_  C  /\  B  C_  C )  <->  ( A  u.  B )  C_  C
)
43biimpi 113 . 2  |-  ( ( A  C_  C  /\  B  C_  C )  -> 
( A  u.  B
)  C_  C )
51, 2, 4syl2anc 391 1  |-  ( ph  ->  ( A  u.  B
)  C_  C )
Colors of variables: wff set class
Syntax hints:    -> wi 4    /\ wa 97    u. cun 2912    C_ wss 2914
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 99  ax-ia2 100  ax-ia3 101  ax-io 630  ax-5 1336  ax-7 1337  ax-gen 1338  ax-ie1 1382  ax-ie2 1383  ax-8 1395  ax-10 1396  ax-11 1397  ax-i12 1398  ax-bndl 1399  ax-4 1400  ax-17 1419  ax-i9 1423  ax-ial 1427  ax-i5r 1428  ax-ext 2022
This theorem depends on definitions:  df-bi 110  df-tru 1246  df-nf 1350  df-sb 1646  df-clab 2027  df-cleq 2033  df-clel 2036  df-nfc 2167  df-v 2556  df-un 2919  df-in 2921  df-ss 2928
This theorem is referenced by:  tpssi  3527  un0addcl  8187  un0mulcl  8188  fzosplit  9000  fzouzsplit  9002  bj-omtrans  9954
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