Metamath Proof Explorer

Theorem nn0xnn0

Description: A standard nonnegative integer is an extended nonnegative integer. (Contributed by AV, 10-Dec-2020)

Ref Expression
Assertion nn0xnn0 
|- ( A e. NN0 -> A e. NN0* )

Proof

Step Hyp Ref Expression
1 nn0ssxnn0 
 |-  NN0 C_ NN0*
2 1 sseli 
 |-  ( A e. NN0 -> A e. NN0* )