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 ) e. NN

Proof

Step	Hyp	Ref	Expression
1		df-base	|- Base = Slot 1
2		1nn	|- 1 e. NN
3	1 2	ndxarg	|- ( Base ` ndx ) = 1
4	3 2	eqeltri	|- ( Base ` ndx ) e. NN