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Theorem unssin 3470
Description: Union as a subset of class complement and intersection (De Morgan's law). One direction of the definition of union in [Mendelson] p. 231. This would be an equality, rather than subset, in classical logic. (Contributed by Jim Kingdon, 25-Jul-2018.)
Assertion
Ref Expression
unssin  |-  ( A  u.  B )  C_  ( _V  \  (
( _V  \  A
)  i^i  ( _V  \  B ) ) )

Proof of Theorem unssin
Dummy variable  x is distinct from all other variables.
StepHypRef Expression
1 oranim 793 . . . . 5  |-  ( ( x  e.  A  \/  x  e.  B )  ->  -.  ( -.  x  e.  A  /\  -.  x  e.  B ) )
2 eldifn 3352 . . . . . 6  |-  ( x  e.  ( _V  \  A )  ->  -.  x  e.  A )
3 eldifn 3352 . . . . . 6  |-  ( x  e.  ( _V  \  B )  ->  -.  x  e.  B )
42, 3anim12i 338 . . . . 5  |-  ( ( x  e.  ( _V 
\  A )  /\  x  e.  ( _V  \  B ) )  -> 
( -.  x  e.  A  /\  -.  x  e.  B ) )
51, 4nsyl 637 . . . 4  |-  ( ( x  e.  A  \/  x  e.  B )  ->  -.  ( x  e.  ( _V  \  A
)  /\  x  e.  ( _V  \  B ) ) )
6 elin 3412 . . . 4  |-  ( x  e.  ( ( _V 
\  A )  i^i  ( _V  \  B
) )  <->  ( x  e.  ( _V  \  A
)  /\  x  e.  ( _V  \  B ) ) )
75, 6sylnibr 688 . . 3  |-  ( ( x  e.  A  \/  x  e.  B )  ->  -.  x  e.  ( ( _V  \  A
)  i^i  ( _V  \  B ) ) )
8 elun 3370 . . 3  |-  ( x  e.  ( A  u.  B )  <->  ( x  e.  A  \/  x  e.  B ) )
9 vex 2824 . . . 4  |-  x  e. 
_V
10 eldif 3229 . . . 4  |-  ( x  e.  ( _V  \ 
( ( _V  \  A )  i^i  ( _V  \  B ) ) )  <->  ( x  e. 
_V  /\  -.  x  e.  ( ( _V  \  A )  i^i  ( _V  \  B ) ) ) )
119, 10mpbiran 953 . . 3  |-  ( x  e.  ( _V  \ 
( ( _V  \  A )  i^i  ( _V  \  B ) ) )  <->  -.  x  e.  ( ( _V  \  A )  i^i  ( _V  \  B ) ) )
127, 8, 113imtr4i 201 . 2  |-  ( x  e.  ( A  u.  B )  ->  x  e.  ( _V  \  (
( _V  \  A
)  i^i  ( _V  \  B ) ) ) )
1312ssriv 3252 1  |-  ( A  u.  B )  C_  ( _V  \  (
( _V  \  A
)  i^i  ( _V  \  B ) ) )
Colors of variables: wff set class
Syntax hints:   -. wn 3    /\ wa 104    \/ wo 720    e. wcel 2209   _Vcvv 2821    \ cdif 3217    u. cun 3218    i^i cin 3219    C_ wss 3220
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-in1 623  ax-in2 624  ax-io 721  ax-5 1500  ax-7 1501  ax-gen 1502  ax-ie1 1546  ax-ie2 1547  ax-8 1557  ax-10 1558  ax-11 1559  ax-i12 1560  ax-bndl 1562  ax-4 1563  ax-17 1579  ax-i9 1583  ax-ial 1587  ax-i5r 1588  ax-ext 2220
This theorem depends on definitions:  df-bi 117  df-tru 1405  df-nf 1514  df-sb 1816  df-clab 2225  df-cleq 2231  df-clel 2234  df-nfc 2381  df-v 2823  df-dif 3222  df-un 3224  df-in 3226  df-ss 3233
This theorem is referenced by: (None)
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