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Definition df-xr 7122
Description: Define the set of extended reals that includes plus and minus infinity. Definition 12-3.1 of [Gleason] p. 173. (Contributed by NM, 13-Oct-2005.)
Assertion
Ref Expression
df-xr  |-  RR*  =  ( RR  u.  { +oo , -oo } )

Detailed syntax breakdown of Definition df-xr
StepHypRef Expression
1 cxr 7117 . 2  class  RR*
2 cr 6945 . . 3  class  RR
3 cpnf 7115 . . . 4  class +oo
4 cmnf 7116 . . . 4  class -oo
53, 4cpr 3403 . . 3  class  { +oo , -oo }
62, 5cun 2942 . 2  class  ( RR  u.  { +oo , -oo } )
71, 6wceq 1259 1  wff  RR*  =  ( RR  u.  { +oo , -oo } )
Colors of variables: wff set class
This definition is referenced by:  ressxr  7127  ltrelxr  7138  pnfxr  8792  mnfxr  8794  elxr  8796  xrex  8856
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