Theorem nnzOLD

Description: Obsolete version of nnz as of 1-Feb-2025. (Contributed by NM, 9-May-2004) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Assertion	nnzOLD	$$⊢N\in \mathbb{N}\to N\in \mathbb{Z}$$

Proof

Step	Hyp	Ref	Expression
1		nnssz	$$⊢\mathbb{N}\subseteq \mathbb{Z}$$
2	1	sseli	$$⊢N\in \mathbb{N}\to N\in \mathbb{Z}$$