Theorem 9cn

Description: The number 9 is a complex number. (Contributed by David A. Wheeler, 8-Dec-2018) Reduce dependencies on axioms. (Revised by Steven Nguyen, 4-Oct-2022)

	Ref	Expression
Assertion	9cn	$$⊢9\in ℂ$$

Proof

Step	Hyp	Ref	Expression
1		df-9	$$⊢9=8+1$$
2		8cn	$$⊢8\in ℂ$$
3		ax-1cn	$$⊢1\in ℂ$$
4	2 3	addcli	$$⊢8+1\in ℂ$$
5	1 4	eqeltri	$$⊢9\in ℂ$$