Theorem 3lt9

Description: 3 is less than 9. (Contributed by Mario Carneiro, 9-Mar-2015)

	Ref	Expression
Assertion	3lt9	|- 3 < 9

Proof

Step	Hyp	Ref	Expression
1		3lt4	|- 3 < 4
2		4lt9	|- 4 < 9
3		3re	|- 3 e. RR
4		4re	|- 4 e. RR
5		9re	|- 9 e. RR
6	3 4 5	lttri	|- ( ( 3 < 4 /\ 4 < 9 ) -> 3 < 9 )
7	1 2 6	mp2an	|- 3 < 9