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	$$class9$$
1		c8	$$class8$$
2		caddc	$$class+$$
3		c1	$$class1$$
4	1 3 2	co	$$class\left(8+1\right)$$
5	0 4	wceq	$$wff9=8+1$$