Definition df-9 9305

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 9297	. 2 class 9
2		c8 9296	. . 3 class 8
3		c1 8130	. . 3 class 1
4		caddc 8132	. . 3 class +
5	2, 3, 4	co 6052	. 2 class ( 8 + 1 )
6	1, 5	wceq 1398	1 wff 9 = ( 8 + 1 )

This definition is referenced by:  9re  9326  9pos  9343  9m1e8  9365  8p1e9  9380  5p4e9  9388  6p3e9  9390  7p2e9  9391  9nn  9408  8lt9  9437  8p2e10  9791  9p9e18  9805  9t9e81  9840  lgsdir2lem5  15922  2lgsoddprmlem3d  16000