Description: Equality theorem for descriptions. Usage of this theorem is discouraged because it depends on ax-13 . (Contributed by Andrew Salmon, 30-Jun-2011) (New usage is discouraged.)
Ref | Expression | ||
---|---|---|---|
Assertion | iotaeq | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | drsb1 | |
|
2 | df-clab | |
|
3 | df-clab | |
|
4 | 1 2 3 | 3bitr4g | |
5 | 4 | eqrdv | |
6 | 5 | eqeq1d | |
7 | 6 | abbidv | |
8 | 7 | unieqd | |
9 | df-iota | |
|
10 | df-iota | |
|
11 | 8 9 10 | 3eqtr4g | |