Definition df-9 8172

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 8163	. 2 class 9
2		c8 8162	. . 3 class 8
3		c1 7044	. . 3 class 1
4		caddc 7046	. . 3 class +
5	2, 3, 4	co 5543	. 2 class ( 8 + 1 )
6	1, 5	wceq 1285	1 wff 9 = ( 8 + 1 )

This definition is referenced by:  9re  8193  9pos  8210  8p1e9  8239  5p4e9  8247  6p3e9  8249  7p2e9  8250  9nn  8267  8lt9  8296  8p2e10  8637  9p9e18  8651  9t9e81  8686