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Theorem difdifdir 4056
Description: Distributive law for class difference. Exercise 4.8 of [Stoll] p. 16. (Contributed by NM, 18-Aug-2004.)
Assertion
Ref Expression
difdifdir  |-  ( ( A  \  B ) 
\  C )  =  ( ( A  \  C )  \  ( B  \  C ) )

Proof of Theorem difdifdir
StepHypRef Expression
1 dif32 3891 . . . . 5  |-  ( ( A  \  B ) 
\  C )  =  ( ( A  \  C )  \  B
)
2 invdif 3868 . . . . 5  |-  ( ( A  \  C )  i^i  ( _V  \  B ) )  =  ( ( A  \  C )  \  B
)
31, 2eqtr4i 2647 . . . 4  |-  ( ( A  \  B ) 
\  C )  =  ( ( A  \  C )  i^i  ( _V  \  B ) )
4 un0 3967 . . . 4  |-  ( ( ( A  \  C
)  i^i  ( _V  \  B ) )  u.  (/) )  =  (
( A  \  C
)  i^i  ( _V  \  B ) )
53, 4eqtr4i 2647 . . 3  |-  ( ( A  \  B ) 
\  C )  =  ( ( ( A 
\  C )  i^i  ( _V  \  B
) )  u.  (/) )
6 indi 3873 . . . 4  |-  ( ( A  \  C )  i^i  ( ( _V 
\  B )  u.  C ) )  =  ( ( ( A 
\  C )  i^i  ( _V  \  B
) )  u.  (
( A  \  C
)  i^i  C )
)
7 disjdif 4040 . . . . . 6  |-  ( C  i^i  ( A  \  C ) )  =  (/)
8 incom 3805 . . . . . 6  |-  ( C  i^i  ( A  \  C ) )  =  ( ( A  \  C )  i^i  C
)
97, 8eqtr3i 2646 . . . . 5  |-  (/)  =  ( ( A  \  C
)  i^i  C )
109uneq2i 3764 . . . 4  |-  ( ( ( A  \  C
)  i^i  ( _V  \  B ) )  u.  (/) )  =  (
( ( A  \  C )  i^i  ( _V  \  B ) )  u.  ( ( A 
\  C )  i^i 
C ) )
116, 10eqtr4i 2647 . . 3  |-  ( ( A  \  C )  i^i  ( ( _V 
\  B )  u.  C ) )  =  ( ( ( A 
\  C )  i^i  ( _V  \  B
) )  u.  (/) )
125, 11eqtr4i 2647 . 2  |-  ( ( A  \  B ) 
\  C )  =  ( ( A  \  C )  i^i  (
( _V  \  B
)  u.  C ) )
13 ddif 3742 . . . . 5  |-  ( _V 
\  ( _V  \  C ) )  =  C
1413uneq2i 3764 . . . 4  |-  ( ( _V  \  B )  u.  ( _V  \ 
( _V  \  C
) ) )  =  ( ( _V  \  B )  u.  C
)
15 indm 3886 . . . . 5  |-  ( _V 
\  ( B  i^i  ( _V  \  C ) ) )  =  ( ( _V  \  B
)  u.  ( _V 
\  ( _V  \  C ) ) )
16 invdif 3868 . . . . . 6  |-  ( B  i^i  ( _V  \  C ) )  =  ( B  \  C
)
1716difeq2i 3725 . . . . 5  |-  ( _V 
\  ( B  i^i  ( _V  \  C ) ) )  =  ( _V  \  ( B 
\  C ) )
1815, 17eqtr3i 2646 . . . 4  |-  ( ( _V  \  B )  u.  ( _V  \ 
( _V  \  C
) ) )  =  ( _V  \  ( B  \  C ) )
1914, 18eqtr3i 2646 . . 3  |-  ( ( _V  \  B )  u.  C )  =  ( _V  \  ( B  \  C ) )
2019ineq2i 3811 . 2  |-  ( ( A  \  C )  i^i  ( ( _V 
\  B )  u.  C ) )  =  ( ( A  \  C )  i^i  ( _V  \  ( B  \  C ) ) )
21 invdif 3868 . 2  |-  ( ( A  \  C )  i^i  ( _V  \ 
( B  \  C
) ) )  =  ( ( A  \  C )  \  ( B  \  C ) )
2212, 20, 213eqtri 2648 1  |-  ( ( A  \  B ) 
\  C )  =  ( ( A  \  C )  \  ( B  \  C ) )
Colors of variables: wff setvar class
Syntax hints:    = wceq 1483   _Vcvv 3200    \ cdif 3571    u. cun 3572    i^i cin 3573   (/)c0 3915
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1722  ax-4 1737  ax-5 1839  ax-6 1888  ax-7 1935  ax-9 1999  ax-10 2019  ax-11 2034  ax-12 2047  ax-13 2246  ax-ext 2602
This theorem depends on definitions:  df-bi 197  df-or 385  df-an 386  df-tru 1486  df-ex 1705  df-nf 1710  df-sb 1881  df-clab 2609  df-cleq 2615  df-clel 2618  df-nfc 2753  df-ral 2917  df-rab 2921  df-v 3202  df-dif 3577  df-un 3579  df-in 3581  df-ss 3588  df-nul 3916
This theorem is referenced by: (None)
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