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Theorem neleqtrrd 2379
Description: If a class is not an element of another class, it is also not an element of an equal class. Deduction form. (Contributed by David Moews, 1-May-2017.)
Hypotheses
Ref Expression
neleqtrrd.1  |-  ( ph  ->  -.  C  e.  B
)
neleqtrrd.2  |-  ( ph  ->  A  =  B )
Assertion
Ref Expression
neleqtrrd  |-  ( ph  ->  -.  C  e.  A
)

Proof of Theorem neleqtrrd
StepHypRef Expression
1 neleqtrrd.1 . 2  |-  ( ph  ->  -.  C  e.  B
)
2 neleqtrrd.2 . . 3  |-  ( ph  ->  A  =  B )
32eleq2d 2350 . 2  |-  ( ph  ->  ( C  e.  A  <->  C  e.  B ) )
41, 3mtbird 292 1  |-  ( ph  ->  -.  C  e.  A
)
Colors of variables: wff set class
Syntax hints:   -. wn 3    -> wi 4    = wceq 1623    e. wcel 1684
This theorem is referenced by:  mreexd  13544  mreexmrid  13545
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8  ax-gen 1533  ax-5 1544  ax-17 1603  ax-9 1635  ax-8 1643  ax-11 1715  ax-ext 2264
This theorem depends on definitions:  df-bi 177  df-an 360  df-ex 1529  df-cleq 2276  df-clel 2279
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