df-un - New Foundations Explorer

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Definition df-un 3214

Description: Define the union of two classes. See elun 3220 for membership. (Contributed by SF, 10-Jan-2015.)

**Assertion**
Ref	Expression
df-un	⊢ (A ∪ B) = ( ∼ A ⩃ ∼ B)

**Detailed syntax breakdown of Definition df-un**
Step	Hyp	Ref	Expression
1		cA	. . 3 class A
2		cB	. . 3 class B
3	1, 2	cun 3207	. 2 class (A ∪ B)
4	1	ccompl 3205	. . 3 class ∼ A
5	2	ccompl 3205	. . 3 class ∼ B
6	4, 5	cnin 3204	. 2 class ( ∼ A ⩃ ∼ B)
7	3, 6	wceq 1642	1 wff (A ∪ B) = ( ∼ A ⩃ ∼ B)

Colors of variables: wff setvar class

This definition is referenced by: elun 3220 nfun 3231 symdifeq1 3248 symdifeq2 3249 dfin5 3545 uncompl 4074 unexg 4101