Definition df-9 8786

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 8778	. 2 class 9
2		c8 8777	. . 3 class 8
3		c1 7621	. . 3 class 1
4		caddc 7623	. . 3 class +
5	2, 3, 4	co 5774	. 2 class ( 8 + 1 )
6	1, 5	wceq 1331	1 wff 9 = ( 8 + 1 )

This definition is referenced by:  9re  8807  9pos  8824  9m1e8  8846  8p1e9  8860  5p4e9  8868  6p3e9  8870  7p2e9  8871  9nn  8888  8lt9  8917  8p2e10  9261  9p9e18  9275  9t9e81  9310