Definition df-9 8689

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 8681	. 2 class 9
2		c8 8680	. . 3 class 8
3		c1 7541	. . 3 class 1
4		caddc 7543	. . 3 class +
5	2, 3, 4	co 5726	. 2 class ( 8 + 1 )
6	1, 5	wceq 1312	1 wff 9 = ( 8 + 1 )

This definition is referenced by:  9re  8710  9pos  8727  8p1e9  8757  5p4e9  8765  6p3e9  8767  7p2e9  8768  9nn  8785  8lt9  8814  8p2e10  9158  9p9e18  9172  9t9e81  9207