Description: Mapping a doubleton word by a function. (Contributed by Mario Carneiro, 27-Feb-2016)
Ref | Expression | ||
---|---|---|---|
Hypotheses | s2co.1 | |
|
s2co.2 | |
||
s2co.3 | |
||
Assertion | s2co | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | s2co.1 | |
|
2 | s2co.2 | |
|
3 | s2co.3 | |
|
4 | df-s2 | |
|
5 | 2 | s1cld | |
6 | s1co | |
|
7 | 2 1 6 | syl2anc | |
8 | df-s2 | |
|
9 | 4 5 3 1 7 8 | cats1co | |