Theorem 6lt9

Description: 6 is less than 9. (Contributed by Mario Carneiro, 9-Mar-2015)

	Ref	Expression
Assertion	6lt9	|- 6 < 9

Proof

Step	Hyp	Ref	Expression
1		6lt7	|- 6 < 7
2		7lt9	|- 7 < 9
3		6re	|- 6 e. RR
4		7re	|- 7 e. RR
5		9re	|- 9 e. RR
6	3 4 5	lttri	|- ( ( 6 < 7 /\ 7 < 9 ) -> 6 < 9 )
7	1 2 6	mp2an	|- 6 < 9