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Definition df-xr 8021
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 8016 . 2  class  RR*
2 cr 7835 . . 3  class  RR
3 cpnf 8014 . . . 4  class +oo
4 cmnf 8015 . . . 4  class -oo
53, 4cpr 3608 . . 3  class  { +oo , -oo }
62, 5cun 3142 . 2  class  ( RR  u.  { +oo , -oo } )
71, 6wceq 1364 1  wff  RR*  =  ( RR  u.  { +oo , -oo } )
Colors of variables: wff set class
This definition is referenced by:  ressxr  8026  pnfxr  8035  mnfxr  8039  ltrelxr  8043  elxr  9801  xrex  9881
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