This is an inofficial mirror of http://metamath.tirix.org for personal testing of a visualizer extension only.

Metamath Proof Explorer

Theorem nn0zi

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

Ref Expression
Hypothesis nn0zi.1 ⊢ 𝑁 ∈ ℕ0
Assertion nn0zi 𝑁 ∈ ℤ

Proof

Step Hyp Ref Expression
1 nn0zi.1 ⊢ 𝑁 ∈ ℕ0
2 nn0ssz ⊢ ℕ0 ⊆ ℤ
3 2 1 sselii ⊢ 𝑁 ∈ ℤ