Theorem basendxnnOLD

Description: Obsolete proof of basendxnn as of 13-Oct-2024. (Contributed by AV, 23-Sep-2020) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Assertion	basendxnnOLD	⊢ ( Base ‘ ndx ) ∈ ℕ

Proof

Step	Hyp	Ref	Expression
1		df-base	⊢ Base = Slot 1
2		1nn	⊢ 1 ∈ ℕ
3	1 2	ndxarg	⊢ ( Base ‘ ndx ) = 1
4	3 2	eqeltri	⊢ ( Base ‘ ndx ) ∈ ℕ