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Definition df-xr 9934
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 9929 . 2 class *
2 cr 9791 . . 3 class
3 cpnf 9927 . . . 4 class +∞
4 cmnf 9928 . . . 4 class -∞
53, 4cpr 4126 . . 3 class {+∞, -∞}
62, 5cun 3537 . 2 class (ℝ ∪ {+∞, -∞})
71, 6wceq 1474 1 wff * = (ℝ ∪ {+∞, -∞})
Colors of variables: wff setvar class
This definition is referenced by:  ressxr  9939  ltrelxr  9950  ssxr  9958  xrex  11663  pnfxr  11783  mnfxr  11785  elxr  11787
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