Definition df-nul 3674

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 3675. (Contributed by NM, 5-Aug-1993.)

Assertion

Ref	Expression
df-nul

Detailed syntax breakdown of Definition df-nul

Step	Hyp	Ref	Expression
1		c0 3673	. 2
2		cvv 3015	. . 3
3	2, 2	cdif 3362	. 2
4	1, 3	wceq 1670	1

This definition is referenced by:  dfnul2  3675  noel  3677