Definition df-9 9370

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 9362	. 2 class 9
2		c8 9361	. . 3 class 8
3		c1 8180	. . 3 class 1
4		caddc 8182	. . 3 class +
5	2, 3, 4	co 6085	. 2 class ( 8 + 1 )
6	1, 5	wceq 1402	1 wff 9 = ( 8 + 1 )

This definition is used by:  9re  9391  9pos  9408  9m1e8  9430  8p1e9  9445  5p4e9  9453  6p3e9  9455  7p2e9  9456  9nn  9473  8lt9  9502  8p2e10  9856  9p9e18  9870  9t9e81  9905  lgsdir2lem5  16151  2lgsoddprmlem3d  16229