Definition df-9 9084

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 9076	. 2 class 9
2		c8 9075	. . 3 class 8
3		c1 7908	. . 3 class 1
4		caddc 7910	. . 3 class +
5	2, 3, 4	co 5934	. 2 class (8 + 1)
6	1, 5	wceq 1372	1 wff 9 = (8 + 1)

This definition is referenced by:  9re  9105  9pos  9122  9m1e8  9144  8p1e9  9159  5p4e9  9167  6p3e9  9169  7p2e9  9170  9nn  9187  8lt9  9216  8p2e10  9565  9p9e18  9579  9t9e81  9614  lgsdir2lem5  15427  2lgsoddprmlem3d  15505