Definition df-9 9073

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 9065	. 2 class 9
2		c8 9064	. . 3 class 8
3		c1 7897	. . 3 class 1
4		caddc 7899	. . 3 class +
5	2, 3, 4	co 5925	. 2 class ( 8 + 1 )
6	1, 5	wceq 1364	1 wff 9 = ( 8 + 1 )

This definition is referenced by:  9re  9094  9pos  9111  9m1e8  9133  8p1e9  9148  5p4e9  9156  6p3e9  9158  7p2e9  9159  9nn  9176  8lt9  9205  8p2e10  9553  9p9e18  9567  9t9e81  9602  lgsdir2lem5  15357  2lgsoddprmlem3d  15435