Description: A group operation maps onto the group's underlying set. (Contributed by NM, 30-Oct-2006) (New usage is discouraged.)
Ref | Expression | ||
---|---|---|---|
Hypothesis | grpfo.1 | |
|
Assertion | grpofo | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | grpfo.1 | |
|
2 | 1 | isgrpo | |
3 | 2 | ibi | |
4 | 3 | simp1d | |
5 | 1 | eqcomi | |
6 | 4 5 | jctir | |
7 | dffo2 | |
|
8 | 6 7 | sylibr | |