Theorem tsetndxnn

Description: The index of the slot for the group operation in an extensible structure is a positive integer. (Contributed by AV, 31-Oct-2024)

	Ref	Expression
Assertion	tsetndxnn	$$⊢\mathrm{TopSet}\left(\mathrm{ndx}\right)\in \mathbb{N}$$

Proof

Step	Hyp	Ref	Expression
1		tsetndx	$$⊢\mathrm{TopSet}\left(\mathrm{ndx}\right)=9$$
2		9nn	$$⊢9\in \mathbb{N}$$
3	1 2	eqeltri	$$⊢\mathrm{TopSet}\left(\mathrm{ndx}\right)\in \mathbb{N}$$