This is an inofficial mirror of http://metamath.tirix.org for personal testing of a visualizer extension only.

Metamath Proof Explorer

Theorem 1nn0

Description: 1 is a nonnegative integer. (Contributed by Raph Levien, 10-Dec-2002)

Ref Expression
Assertion 1nn0 
|- 1 e. NN0

Proof

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