theorem mul11 (a: nat): $ 1 * a = a $;
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | eqtr | 1 * a = a * 1 -> a * 1 = a -> 1 * a = a |
|
2 | mulcom | 1 * a = a * 1 |
|
3 | 1, 2 | ax_mp | a * 1 = a -> 1 * a = a |
4 | mul12 | a * 1 = a |
|
5 | 3, 4 | ax_mp | 1 * a = a |