Definition df-9 9137

Description: Define the number 9. (Contributed by NM, 27-May-1999.)

Assertion

Ref	Expression
df-9	|- 9 = ( 8 + 1 )

Detailed syntax breakdown of Definition df-9

Step	Hyp	Ref	Expression
1		c9 9129	. 2 class 9
2		c8 9128	. . 3 class 8
3		c1 7961	. . 3 class 1
4		caddc 7963	. . 3 class +
5	2, 3, 4	co 5967	. 2 class ( 8 + 1 )
6	1, 5	wceq 1373	1 wff 9 = ( 8 + 1 )

This definition is referenced by:  9re  9158  9pos  9175  9m1e8  9197  8p1e9  9212  5p4e9  9220  6p3e9  9222  7p2e9  9223  9nn  9240  8lt9  9269  8p2e10  9618  9p9e18  9632  9t9e81  9667  lgsdir2lem5  15624  2lgsoddprmlem3d  15702