Description: Equality theorem for onto functions. (Contributed by NM, 1-Aug-1994)
Ref | Expression | ||
---|---|---|---|
Assertion | foeq1 | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | fneq1 | |
|
2 | rneq | |
|
3 | 2 | eqeq1d | |
4 | 1 3 | anbi12d | |
5 | df-fo | |
|
6 | df-fo | |
|
7 | 4 5 6 | 3bitr4g | |