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Definition df-nul 3363
Description: Define the empty set. Special case of Exercise 4.10(o) of [Mendelson] p. 231. For a more traditional definition, but requiring a dummy variable, see dfnul2 3364. (Contributed by NM, 5-Aug-1993.)
Assertion
Ref Expression
df-nul  |-  (/)  =  ( _V  \  _V )

Detailed syntax breakdown of Definition df-nul
StepHypRef Expression
1 c0 3362 . 2  class  (/)
2 cvv 2727 . . 3  class  _V
32, 2cdif 3075 . 2  class  ( _V 
\  _V )
41, 3wceq 1619 1  wff  (/)  =  ( _V  \  _V )
Colors of variables: wff set class
This definition is referenced by:  dfnul2  3364  noel  3366
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