Definition df-nul 3410

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 3411. (Contributed by NM, 5-Aug-1993.)

Assertion

Ref	Expression
df-nul	|- (/) = ( _V \ _V )

Detailed syntax breakdown of Definition df-nul

Step	Hyp	Ref	Expression
1		c0 3409	. 2 class (/)
2		cvv 2726	. . 3 class _V
3	2, 2	cdif 3113	. 2 class ( _V \ _V )
4	1, 3	wceq 1343	1 wff (/) = ( _V \ _V )

This definition is referenced by:  dfnul2  3411  noel  3413  bdcnulALT  13748