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 ∈ ℂ

Proof

Step	Hyp	Ref	Expression
1		df-9	⊢ 9 = ( 8 + 1 )
2		8cn	⊢ 8 ∈ ℂ
3		ax-1cn	⊢ 1 ∈ ℂ
4	2 3	addcli	⊢ ( 8 + 1 ) ∈ ℂ
5	1 4	eqeltri	⊢ 9 ∈ ℂ