Theorem nnssq

Description: The positive integers are a subset of the rationals. (Contributed by NM, 31-Jul-2004)

	Ref	Expression
Assertion	nnssq	⊢ ℕ ⊆ ℚ

Proof

Step	Hyp	Ref	Expression
1		nnssz	⊢ ℕ ⊆ ℤ
2		zssq	⊢ ℤ ⊆ ℚ
3	1 2	sstri	⊢ ℕ ⊆ ℚ