Question

How do I find the value of cos 7π?

Answer 1

`cos 7 pi = -1`

Explanation:

You may know that `Cos 0 = 1` and `cos pi = -1`
If you keep adding `2 pi` to the angle, the value doesn't change
So, `cos pi + 2 pi = cos 3 * pi` is also = - 1. Similarly, `cos 5 * pi, cos 7 * pi, cos 9 * pi` etc. in general `cos (2 * n + 1) * pi`, where n is an integer like 1, 2, 3, etc, are -1