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Definition df-xr 9057
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 9052 . 2  class  RR*
2 cr 8922 . . 3  class  RR
3 cpnf 9050 . . . 4  class  +oo
4 cmnf 9051 . . . 4  class  -oo
53, 4cpr 3758 . . 3  class  {  +oo , 
-oo }
62, 5cun 3261 . 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  9062  ltrelxr  9072  ssxr  9078  xrex  10541  pnfxr  10645  mnfxr  10646  elxr  10648
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