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Definition df-xr 7429
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 7424 . 2 class *
2 cr 7252 . . 3 class
3 cpnf 7422 . . . 4 class +∞
4 cmnf 7423 . . . 4 class -∞
53, 4cpr 3423 . . 3 class {+∞, -∞}
62, 5cun 2982 . 2 class (ℝ ∪ {+∞, -∞})
71, 6wceq 1285 1 wff * = (ℝ ∪ {+∞, -∞})
Colors of variables: wff set class
This definition is referenced by:  ressxr  7434  pnfxr  7443  mnfxr  7447  ltrelxr  7450  elxr  9142  xrex  9200
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