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

Metamath Proof Explorer

Theorem neg1z

Description: -1 is an integer. (Contributed by David A. Wheeler, 5-Dec-2018)

Ref Expression
Assertion neg1z 
|- -u 1 e. ZZ

Proof

Step Hyp Ref Expression
1 1nn 
 |-  1 e. NN
2 nnnegz 
 |-  ( 1 e. NN -> -u 1 e. ZZ )
3 1 2 ax-mp 
 |-  -u 1 e. ZZ