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Definition df-un 2992
Description: Define the union of two classes. Definition 5.6 of [TakeutiZaring] p. 16. Contrast this operation with difference (𝐴𝐵) (df-dif 2990) and intersection (𝐴𝐵) (df-in 2994). (Contributed by NM, 23-Aug-1993.)
Assertion
Ref Expression
df-un (𝐴𝐵) = {𝑥 ∣ (𝑥𝐴𝑥𝐵)}
Distinct variable groups:   𝑥,𝐴   𝑥,𝐵

Detailed syntax breakdown of Definition df-un
StepHypRef Expression
1 cA . . 3 class 𝐴
2 cB . . 3 class 𝐵
31, 2cun 2986 . 2 class (𝐴𝐵)
4 vx . . . . . 6 setvar 𝑥
54cv 1286 . . . . 5 class 𝑥
65, 1wcel 1436 . . . 4 wff 𝑥𝐴
75, 2wcel 1436 . . . 4 wff 𝑥𝐵
86, 7wo 662 . . 3 wff (𝑥𝐴𝑥𝐵)
98, 4cab 2071 . 2 class {𝑥 ∣ (𝑥𝐴𝑥𝐵)}
103, 9wceq 1287 1 wff (𝐴𝐵) = {𝑥 ∣ (𝑥𝐴𝑥𝐵)}
Colors of variables: wff set class
This definition is referenced by:  elun  3130  nfun  3145  unipr  3650  iinuniss  3793  bdcun  11198
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