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Mirrors > Home > ILE Home > Th. List > df-nul | GIF version |
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 3226. (Contributed by NM, 5-Aug-1993.) |
Ref | Expression |
---|---|
df-nul | ⊢ ∅ = (V ∖ V) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | c0 3224 | . 2 class ∅ | |
2 | cvv 2557 | . . 3 class V | |
3 | 2, 2 | cdif 2914 | . 2 class (V ∖ V) |
4 | 1, 3 | wceq 1243 | 1 wff ∅ = (V ∖ V) |
Colors of variables: wff set class |
This definition is referenced by: dfnul2 3226 noel 3228 bdcnulALT 9986 |
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