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Definition df-xr 9126
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 9121 . 2  class  RR*
2 cr 8991 . . 3  class  RR
3 cpnf 9119 . . . 4  class  +oo
4 cmnf 9120 . . . 4  class  -oo
53, 4cpr 3817 . . 3  class  {  +oo , 
-oo }
62, 5cun 3320 . 2  class  ( RR  u.  {  +oo ,  -oo } )
71, 6wceq 1653 1  wff  RR*  =  ( RR  u.  {  +oo , 
-oo } )
Colors of variables: wff set class
This definition is referenced by:  ressxr  9131  ltrelxr  9141  ssxr  9147  xrex  10611  pnfxr  10715  mnfxr  10716  elxr  10718
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