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Metamath Proof Explorer

Theorem nnssz

Description: Positive integers are a subset of integers. (Contributed by NM, 9-Jan-2002)

Ref Expression
Assertion nnssz ℕ ⊆ ℤ

Proof

Step Hyp Ref Expression
1 nnz ⊢ ( 𝑥 ∈ ℕ → 𝑥 ∈ ℤ )
2 1 ssriv ⊢ ℕ ⊆ ℤ