Description: Obsolete version of ccat2s1len as of 14-Jan-2024. The length of the concatenation of two singleton words. (Contributed by Alexander van der Vekens, 22-Sep-2018) (Proof modification is discouraged.) (New usage is discouraged.)
Ref | Expression | ||
---|---|---|---|
Assertion | ccat2s1lenOLD | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | s1cl | |
|
2 | s1cl | |
|
3 | ccatlenOLD | |
|
4 | s1len | |
|
5 | s1len | |
|
6 | 4 5 | oveq12i | |
7 | 1p1e2 | |
|
8 | 6 7 | eqtri | |
9 | 3 8 | eqtrdi | |
10 | 1 2 9 | syl2an | |