Definition df-9 7980

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 7971	. 2 class 9
2		c8 7970	. . 3 class 8
3		c1 6890	. . 3 class 1
4		caddc 6892	. . 3 class +
5	2, 3, 4	co 5512	. 2 class (8 + 1)
6	1, 5	wceq 1243	1 wff 9 = (8 + 1)

This definition is referenced by:  9re  8002  9pos  8020  8p1e9  8050  5p4e9  8059  6p3e9  8062  7p2e9  8064  8p2e10  8066  9nn  8084  8lt9  8114  9p9e18  8436  9t9e81  8469