Theorem nn0zi

Description: A nonnegative integer is an integer. (Contributed by Mario Carneiro, 18-Feb-2014)

	Ref	Expression
Hypothesis	nn0zi.1	$$⊢N\in {\mathbb{N}}_0$$
Assertion	nn0zi	$$⊢N\in \mathbb{Z}$$

Proof

Step	Hyp	Ref	Expression
1		nn0zi.1	$$⊢N\in {\mathbb{N}}_0$$
2		nn0ssz	$$⊢{\mathbb{N}}_0\subseteq \mathbb{Z}$$
3	2 1	sselii	$$⊢N\in \mathbb{Z}$$