Description: 1 is an identity element for multiplication on positive integers. (Contributed by NM, 4-Mar-1996) (Revised by Mario Carneiro, 17-Nov-2014) (New usage is discouraged.)
Ref | Expression | ||
---|---|---|---|
Assertion | mulidpi | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | 1pi | |
|
2 | mulpiord | |
|
3 | 1 2 | mpan2 | |
4 | pinn | |
|
5 | nnm1 | |
|
6 | 4 5 | syl | |
7 | 3 6 | eqtrd | |