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	$$⊢{\mathrm{Base}}_{\mathrm{ndx}}\in \mathbb{N}$$

Proof

Step	Hyp	Ref	Expression
1		df-base	$$⊢\mathrm{Base}=\mathrm{Slot}1$$
2		1nn	$$⊢1\in \mathbb{N}$$
3	1 2	ndxarg	$$⊢{\mathrm{Base}}_{\mathrm{ndx}}=1$$
4	3 2	eqeltri	$$⊢{\mathrm{Base}}_{\mathrm{ndx}}\in \mathbb{N}$$