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Definition df-xr 10668
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 10663 . 2 class *
2 cr 10525 . . 3 class
3 cpnf 10661 . . . 4 class +∞
4 cmnf 10662 . . . 4 class -∞
53, 4cpr 4541 . . 3 class {+∞, -∞}
62, 5cun 3906 . 2 class (ℝ ∪ {+∞, -∞})
71, 6wceq 1538 1 wff * = (ℝ ∪ {+∞, -∞})
Colors of variables: wff setvar class
This definition is referenced by:  ressxr  10674  pnfxr  10684  mnfxr  10687  ltrelxr  10691  ssxr  10699  xrex  12374  elxr  12499  climxlim2lem  42426
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