Metamath Proof Explorer

Theorem nnssq

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

Ref Expression
Assertion nnssq 
|- NN C_ QQ

Proof

Step Hyp Ref Expression
1 nnssz 
 |-  NN C_ ZZ
2 zssq 
 |-  ZZ C_ QQ
3 1 2 sstri 
 |-  NN C_ QQ