Description: A restricted class abstraction with a unique member can be expressed as a singleton. (Contributed by NM, 30-May-2006)
Ref | Expression | ||
---|---|---|---|
Assertion | snriota | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | df-reu | |
|
2 | sniota | |
|
3 | 1 2 | sylbi | |
4 | df-rab | |
|
5 | df-riota | |
|
6 | 5 | sneqi | |
7 | 3 4 6 | 3eqtr4g | |