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Definition df-xnn0 8670
Description: Define the set of extended nonnegative integers that includes positive infinity. Analogue of the extension of the real numbers  RR*, see df-xr 7470. If we assumed excluded middle, this would be essentially the same as ℕ as defined at df-nninf 6735 but in its absence the relationship between the two is more complicated. (Contributed by AV, 10-Dec-2020.)
Assertion
Ref Expression
df-xnn0  |- NN0*  =  ( NN0  u.  { +oo } )

Detailed syntax breakdown of Definition df-xnn0
StepHypRef Expression
1 cxnn0 8669 . 2  class NN0*
2 cn0 8606 . . 3  class  NN0
3 cpnf 7463 . . . 4  class +oo
43csn 3431 . . 3  class  { +oo }
52, 4cun 2986 . 2  class  ( NN0 
u.  { +oo } )
61, 5wceq 1287 1  wff NN0*  =  ( NN0  u.  { +oo } )
Colors of variables: wff set class
This definition is referenced by:  elxnn0  8671  nn0ssxnn0  8672  fxnn0nninf  9772
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