Definition df-9 8944

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 8936	. 2 class 9
2		c8 8935	. . 3 class 8
3		c1 7775	. . 3 class 1
4		caddc 7777	. . 3 class +
5	2, 3, 4	co 5853	. 2 class ( 8 + 1 )
6	1, 5	wceq 1348	1 wff 9 = ( 8 + 1 )

This definition is referenced by:  9re  8965  9pos  8982  9m1e8  9004  8p1e9  9018  5p4e9  9026  6p3e9  9028  7p2e9  9029  9nn  9046  8lt9  9075  8p2e10  9422  9p9e18  9436  9t9e81  9471  lgsdir2lem5  13727