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Definition df-xr 8058
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 * = (ℝ ∪ {+∞, -∞})

Detailed syntax breakdown of Definition df-xr
StepHypRef Expression
1 cxr 8053 . 2 class *
2 cr 7871 . . 3 class
3 cpnf 8051 . . . 4 class +∞
4 cmnf 8052 . . . 4 class -∞
53, 4cpr 3619 . . 3 class {+∞, -∞}
62, 5cun 3151 . 2 class (ℝ ∪ {+∞, -∞})
71, 6wceq 1364 1 wff * = (ℝ ∪ {+∞, -∞})
Colors of variables: wff set class
This definition is referenced by:  ressxr  8063  pnfxr  8072  mnfxr  8076  ltrelxr  8080  elxr  9842  xrex  9922
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