Description: Class abstraction in a subclass relationship. (Contributed by Glauco Siliprandi, 26-Jun-2021)
Ref | Expression | ||
---|---|---|---|
Hypothesis | abssf.1 | ||
Assertion | abssf |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | abssf.1 | ||
2 | 1 | abid2f | |
3 | 2 | sseq2i | |
4 | ss2ab | ||
5 | 3 4 | bitr3i |