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Definition df-xr 9080
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 9075 . 2  class  RR*
2 cr 8945 . . 3  class  RR
3 cpnf 9073 . . . 4  class  +oo
4 cmnf 9074 . . . 4  class  -oo
53, 4cpr 3775 . . 3  class  {  +oo , 
-oo }
62, 5cun 3278 . 2  class  ( RR  u.  {  +oo ,  -oo } )
71, 6wceq 1649 1  wff  RR*  =  ( RR  u.  {  +oo , 
-oo } )
Colors of variables: wff set class
This definition is referenced by:  ressxr  9085  ltrelxr  9095  ssxr  9101  xrex  10565  pnfxr  10669  mnfxr  10670  elxr  10672
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