Definition df-9

Description: Define the number 9. (Contributed by NM, 27-May-1999)

	Ref	Expression
Assertion	df-9	⊢ 9 = ( 8 + 1 )

Detailed syntax breakdown

Step	Hyp	Ref	Expression
0		c9	⊢ 9
1		c8	⊢ 8
2		caddc	⊢ +
3		c1	⊢ 1
4	1 3 2	co	⊢ ( 8 + 1 )
5	0 4	wceq	⊢ 9 = ( 8 + 1 )