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Definition df-nul 3638
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 3639. (Contributed by NM, 17-Jun-1993.)
Assertion
Ref Expression
df-nul

Detailed syntax breakdown of Definition df-nul
StepHypRef Expression
1 c0 3637 . 2
2 cvv 2972 . . 3
32, 2cdif 3325 . 2
41, 3wceq 1369 1
Colors of variables: wff setvar class
This definition is referenced by:  dfnul2  3639  noel  3641
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