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Mirrors > Home > ILE Home > Th. List > df-nul | Unicode 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 3416. (Contributed by NM, 5-Aug-1993.) |
Ref | Expression |
---|---|
df-nul |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | c0 3414 | . 2 | |
2 | cvv 2730 | . . 3 | |
3 | 2, 2 | cdif 3118 | . 2 |
4 | 1, 3 | wceq 1348 | 1 |
Colors of variables: wff set class |
This definition is referenced by: dfnul2 3416 noel 3418 bdcnulALT 13901 |
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