Definition df-xr 5501

Description: Define the set of extended reals that includes plus and minus infinity. Definition 12-3.1 of [Gleason] p. 173.

Assertion

Ref	Expression
df-xr	|- RR* = (RR u. { +oo, -oo})

Detailed syntax breakdown of Definition df-xr

Step	Hyp	Ref	Expression
1		cxr 5497	. 2 class RR*
2		cr 5245	. . 3 class RR
3		cpnf 5495	. . . 4 class +oo
4		cmnf 5496	. . . 4 class -oo
5	3, 4	cpr 2414	. . 3 class { +oo, -oo}
6	2, 5	cun 2048	. 2 class (RR u. { +oo, -oo})
7	1, 6	wceq 958	1 wff RR* = (RR u. { +oo, -oo})

This definition is referenced by:  xrex 5504  pnfxr 5505  mnfxr 5506  ressxr 5510  elxr 5547  ssxr 5552

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