Description: Equality theorem for singletons. Part of Exercise 4 of TakeutiZaring p. 15. (Contributed by NM, 21-Jun-1993)
Ref | Expression | ||
---|---|---|---|
Assertion | sneq | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | eqeq2 | |
|
2 | 1 | abbidv | |
3 | df-sn | |
|
4 | df-sn | |
|
5 | 2 3 4 | 3eqtr4g | |