Description: Value of the cosine function at 0. (Contributed by NM, 30-Apr-2005)
Ref | Expression | ||
---|---|---|---|
Assertion | cos0 | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | 0re | |
|
2 | recosval | |
|
3 | 1 2 | ax-mp | |
4 | it0e0 | |
|
5 | 4 | fveq2i | |
6 | ef0 | |
|
7 | 5 6 | eqtri | |
8 | 7 | fveq2i | |
9 | re1 | |
|
10 | 8 9 | eqtri | |
11 | 3 10 | eqtri | |