Definition df-xr 9668

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	|- RR* = ( RR u. { +oo , -oo } )

Detailed syntax breakdown of Definition df-xr

Step	Hyp	Ref	Expression
1		cxr 9663	. 2 class RR*
2		cr 9527	. . 3 class RR
3		cpnf 9661	. . . 4 class +oo
4		cmnf 9662	. . . 4 class -oo
5	3, 4	cpr 3995	. . 3 class { +oo , -oo }
6	2, 5	cun 3431	. 2 class ( RR u. { +oo , -oo } )
7	1, 6	wceq 1437	1 wff RR* = ( RR u. { +oo , -oo } )

This definition is referenced by:  ressxr  9673  ltrelxr  9684  ssxr  9692  xrex  11288  pnfxr  11401  mnfxr  11403  elxr  11405