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Definition df-xr 6861
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 6856 . 2  RR*
2 cr 6710 . . 3  RR
3 cpnf 6854 . . . 4 +oo
4 cmnf 6855 . . . 4 -oo
53, 4cpr 3368 . . 3  { +oo , -oo }
62, 5cun 2909 . 2  RR  u.  { +oo , -oo }
71, 6wceq 1242 1  RR*  RR  u.  { +oo , -oo }
Colors of variables: wff set class
This definition is referenced by:  ressxr  6866  ltrelxr  6877  pnfxr  8462  mnfxr  8464  elxr  8466  xrex  8526
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