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Theorem difeq12i 3620
Description: Equality inference for class difference. (Contributed by NM, 29-Aug-2004.)
Hypotheses
Ref Expression
difeq1i.1  |-  A  =  B
difeq12i.2  |-  C  =  D
Assertion
Ref Expression
difeq12i  |-  ( A 
\  C )  =  ( B  \  D
)

Proof of Theorem difeq12i
StepHypRef Expression
1 difeq1i.1 . . 3  |-  A  =  B
21difeq1i 3618 . 2  |-  ( A 
\  C )  =  ( B  \  C
)
3 difeq12i.2 . . 3  |-  C  =  D
43difeq2i 3619 . 2  |-  ( B 
\  C )  =  ( B  \  D
)
52, 4eqtri 2496 1  |-  ( A 
\  C )  =  ( B  \  D
)
Colors of variables: wff setvar class
Syntax hints:    = wceq 1379    \ cdif 3473
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1601  ax-4 1612  ax-5 1680  ax-6 1719  ax-7 1739  ax-10 1786  ax-11 1791  ax-12 1803  ax-13 1968  ax-ext 2445
This theorem depends on definitions:  df-bi 185  df-an 371  df-tru 1382  df-ex 1597  df-nf 1600  df-sb 1712  df-clab 2453  df-cleq 2459  df-clel 2462  df-nfc 2617  df-ral 2819  df-rab 2823  df-dif 3479
This theorem is referenced by:  difrab  3772  uniioombllem4  21727  zrdivrng  25107  gtiso  27188  preddif  28845  dvtanlem  29639  isdrngo1  29960  pwfi2f1o  30648
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