theorem zadd01 (a: nat): $ 0 +Z a = a $;
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | eqtr | 0 +Z a = a +Z 0 -> a +Z 0 = a -> 0 +Z a = a |
|
2 | zaddcom | 0 +Z a = a +Z 0 |
|
3 | 1, 2 | ax_mp | a +Z 0 = a -> 0 +Z a = a |
4 | zadd02 | a +Z 0 = a |
|
5 | 3, 4 | ax_mp | 0 +Z a = a |