Definition df-xr 11325

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* = (ℝ ∪ {+∞, -∞})

Detailed syntax breakdown of Definition df-xr

Step	Hyp	Ref	Expression
1		cxr 11320	. 2 class ℝ*
2		cr 11177	. . 3 class ℝ
3		cpnf 11318	. . . 4 class +∞
4		cmnf 11319	. . . 4 class -∞
5	3, 4	cpr 4586	. . 3 class {+∞, -∞}
6	2, 5	cun 3897	. 2 class (ℝ ∪ {+∞, -∞})
7	1, 6	wceq 1570	1 wff ℝ* = (ℝ ∪ {+∞, -∞})

This definition is used by:  ressxr  11331  pnfxr  11341  mnfxr  11344  ltrelxr  11348  ssxr  11357  xrex  13093  elxr  13223  climxlim2lem  46796