Definition df-9 9075

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 9067	. 2 class 9
2		c8 9066	. . 3 class 8
3		c1 7899	. . 3 class 1
4		caddc 7901	. . 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  9096  9pos  9113  9m1e8  9135  8p1e9  9150  5p4e9  9158  6p3e9  9160  7p2e9  9161  9nn  9178  8lt9  9207  8p2e10  9555  9p9e18  9569  9t9e81  9604  lgsdir2lem5  15381  2lgsoddprmlem3d  15459