Definition df-nul 2876

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 2877.

Assertion

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

Detailed syntax breakdown of Definition df-nul

Step	Hyp	Ref	Expression
1		c0 2875	. 2 class (/)
2		cvv 2292	. . 3 class _V
3	2, 2	cdif 2590	. 2 class (_V \ _V)
4	1, 3	wceq 1298	1 wff (/) = (_V \ _V)

This definition is referenced by:  dfnul2 2877

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