Definition df-9 8923

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 8915	. 2 class 9
2		c8 8914	. . 3 class 8
3		c1 7754	. . 3 class 1
4		caddc 7756	. . 3 class +
5	2, 3, 4	co 5842	. 2 class ( 8 + 1 )
6	1, 5	wceq 1343	1 wff 9 = ( 8 + 1 )

This definition is referenced by:  9re  8944  9pos  8961  9m1e8  8983  8p1e9  8997  5p4e9  9005  6p3e9  9007  7p2e9  9008  9nn  9025  8lt9  9054  8p2e10  9401  9p9e18  9415  9t9e81  9450  lgsdir2lem5  13573