Database
REAL AND COMPLEX NUMBERS
Integer sets
Integers (as a subset of complex numbers)
nnssz
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nn0ssz
Metamath Proof Explorer
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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