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Definition df-xr 9628
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 9623 . 2  class  RR*
2 cr 9487 . . 3  class  RR
3 cpnf 9621 . . . 4  class +oo
4 cmnf 9622 . . . 4  class -oo
53, 4cpr 4029 . . 3  class  { +oo , -oo }
62, 5cun 3474 . 2  class  ( RR  u.  { +oo , -oo } )
71, 6wceq 1379 1  wff  RR*  =  ( RR  u.  { +oo , -oo } )
Colors of variables: wff setvar class
This definition is referenced by:  ressxr  9633  ltrelxr  9644  ssxr  9650  xrex  11213  pnfxr  11317  mnfxr  11319  elxr  11321
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