Metamath Proof Explorer

Theorem 9nn0

Description: 9 is a nonnegative integer. (Contributed by Mario Carneiro, 19-Apr-2015)

Ref Expression
Assertion 9nn0 
|- 9 e. NN0

Proof

Step Hyp Ref Expression
1 9nn 
 |-  9 e. NN
2 1 nnnn0i 
 |-  9 e. NN0