Theorem nn0z

Description: A nonnegative integer is an integer. (Contributed by NM, 9-May-2004)

	Ref	Expression
Assertion	nn0z	$$⊢N\in {\mathbb{N}}_0\to N\in \mathbb{Z}$$

Proof

Step	Hyp	Ref	Expression
1		nn0ssz	$$⊢{\mathbb{N}}_0\subseteq \mathbb{Z}$$
2	1	sseli	$$⊢N\in {\mathbb{N}}_0\to N\in \mathbb{Z}$$