Definition df-9 9102

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 9094	. 2 class 9
2		c8 9093	. . 3 class 8
3		c1 7926	. . 3 class 1
4		caddc 7928	. . 3 class +
5	2, 3, 4	co 5944	. 2 class ( 8 + 1 )
6	1, 5	wceq 1373	1 wff 9 = ( 8 + 1 )

This definition is referenced by:  9re  9123  9pos  9140  9m1e8  9162  8p1e9  9177  5p4e9  9185  6p3e9  9187  7p2e9  9188  9nn  9205  8lt9  9234  8p2e10  9583  9p9e18  9597  9t9e81  9632  lgsdir2lem5  15509  2lgsoddprmlem3d  15587