Description: A singleton is a subset of an unordered triple containing its member. (Contributed by NM, 9-Oct-2013)
Ref | Expression | ||
---|---|---|---|
Assertion | snsstp2 | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | snsspr2 | |
|
2 | ssun1 | |
|
3 | 1 2 | sstri | |
4 | df-tp | |
|
5 | 3 4 | sseqtrri | |