Theorem 4lt9

Description: 4 is less than 9. (Contributed by Mario Carneiro, 9-Mar-2015)

	Ref	Expression
Assertion	4lt9	|- 4 < 9

Proof

Step	Hyp	Ref	Expression
1		4lt5	|- 4 < 5
2		5lt9	|- 5 < 9
3		4re	|- 4 e. RR
4		5re	|- 5 e. RR
5		9re	|- 9 e. RR
6	3 4 5	lttri	|- ( ( 4 < 5 /\ 5 < 9 ) -> 4 < 9 )
7	1 2 6	mp2an	|- 4 < 9