Definition df-9 9172

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 9164	. 2 class 9
2		c8 9163	. . 3 class 8
3		c1 7996	. . 3 class 1
4		caddc 7998	. . 3 class +
5	2, 3, 4	co 6000	. 2 class (8 + 1)
6	1, 5	wceq 1395	1 wff 9 = (8 + 1)

This definition is referenced by:  9re  9193  9pos  9210  9m1e8  9232  8p1e9  9247  5p4e9  9255  6p3e9  9257  7p2e9  9258  9nn  9275  8lt9  9304  8p2e10  9653  9p9e18  9667  9t9e81  9702  lgsdir2lem5  15705  2lgsoddprmlem3d  15783