Definition df-9 9101

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 9093	. 2 class 9
2		c8 9092	. . 3 class 8
3		c1 7925	. . 3 class 1
4		caddc 7927	. . 3 class +
5	2, 3, 4	co 5943	. 2 class (8 + 1)
6	1, 5	wceq 1372	1 wff 9 = (8 + 1)

This definition is referenced by:  9re  9122  9pos  9139  9m1e8  9161  8p1e9  9176  5p4e9  9184  6p3e9  9186  7p2e9  9187  9nn  9204  8lt9  9233  8p2e10  9582  9p9e18  9596  9t9e81  9631  lgsdir2lem5  15451  2lgsoddprmlem3d  15529