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	$$⊢3\in ℝ$$
4		4re	$$⊢4\in ℝ$$
5		9re	$$⊢9\in ℝ$$
6	3 4 5	lttri	$$⊢\left(3<4\wedge 4<9\right)\to 3<9$$
7	1 2 6	mp2an	$$⊢3<9$$