Theorem iccleub

Description: An element of a closed interval is less than or equal to its upper bound. (Contributed by Jeff Hankins, 14-Jul-2009)

	Ref	Expression
Assertion	iccleub	|- ( ( A e. RR* /\ B e. RR* /\ C e. ( A [,] B ) ) -> C <_ B )

Proof

Step	Hyp	Ref	Expression
1		elicc1	|- ( ( A e. RR* /\ B e. RR* ) -> ( C e. ( A [,] B ) <-> ( C e. RR* /\ A <_ C /\ C <_ B ) ) )
2		simp3	|- ( ( C e. RR* /\ A <_ C /\ C <_ B ) -> C <_ B )
3	1 2	syl6bi	|- ( ( A e. RR* /\ B e. RR* ) -> ( C e. ( A [,] B ) -> C <_ B ) )
4	3	3impia	|- ( ( A e. RR* /\ B e. RR* /\ C e. ( A [,] B ) ) -> C <_ B )