Definition df-9 8985

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 8977	. 2 class 9
2		c8 8976	. . 3 class 8
3		c1 7812	. . 3 class 1
4		caddc 7814	. . 3 class +
5	2, 3, 4	co 5875	. 2 class ( 8 + 1 )
6	1, 5	wceq 1353	1 wff 9 = ( 8 + 1 )

This definition is referenced by:  9re  9006  9pos  9023  9m1e8  9045  8p1e9  9059  5p4e9  9067  6p3e9  9069  7p2e9  9070  9nn  9087  8lt9  9116  8p2e10  9463  9p9e18  9477  9t9e81  9512  lgsdir2lem5  14436  2lgsoddprmlem3d  14461