Definition df-9 9209

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 9201	. 2 class 9
2		c8 9200	. . 3 class 8
3		c1 8033	. . 3 class 1
4		caddc 8035	. . 3 class +
5	2, 3, 4	co 6018	. 2 class ( 8 + 1 )
6	1, 5	wceq 1397	1 wff 9 = ( 8 + 1 )

This definition is referenced by:  9re  9230  9pos  9247  9m1e8  9269  8p1e9  9284  5p4e9  9292  6p3e9  9294  7p2e9  9295  9nn  9312  8lt9  9341  8p2e10  9690  9p9e18  9704  9t9e81  9739  lgsdir2lem5  15780  2lgsoddprmlem3d  15858