Theorem iccssxr

Description: A closed interval is a set of extended reals. (Contributed by FL, 28-Jul-2008) (Revised by Mario Carneiro, 4-Jul-2014)

	Ref	Expression
Assertion	iccssxr	|- ( A [,] B ) C_ RR*

Proof

Step	Hyp	Ref	Expression
1		df-icc	|- [,] = ( x e. RR* , y e. RR* |-> { z e. RR* | ( x <_ z /\ z <_ y ) } )
2	1	ixxssxr	|- ( A [,] B ) C_ RR*