Definition df-9 9104

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 9096	. 2 class 9
2		c8 9095	. . 3 class 8
3		c1 7928	. . 3 class 1
4		caddc 7930	. . 3 class +
5	2, 3, 4	co 5946	. 2 class ( 8 + 1 )
6	1, 5	wceq 1373	1 wff 9 = ( 8 + 1 )

This definition is referenced by:  9re  9125  9pos  9142  9m1e8  9164  8p1e9  9179  5p4e9  9187  6p3e9  9189  7p2e9  9190  9nn  9207  8lt9  9236  8p2e10  9585  9p9e18  9599  9t9e81  9634  lgsdir2lem5  15542  2lgsoddprmlem3d  15620