Theorem plusgndxnn

Description: The index of the slot for the group operation in an extensible structure is a positive integer. (Contributed by AV, 17-Oct-2024)

	Ref	Expression
Assertion	plusgndxnn	⊢ ( +g ‘ ndx ) ∈ ℕ

Proof

Step	Hyp	Ref	Expression
1		plusgndx	⊢ ( +g ‘ ndx ) = 2
2		2nn	⊢ 2 ∈ ℕ
3	1 2	eqeltri	⊢ ( +g ‘ ndx ) ∈ ℕ