Question

Explain why cos(−3π4)=cos(5π4).

Answer 1

See below

Explanation:

Think about what happens when you rotate around a circle
`-(3\pi)/(4)` radians. This means that you are going clockwise
`-(3\pi)/(4)` radians.

Likewise, if you went
`(5\pi)/(4)` radians counterclockwise, you'd end up in the same place, so the cosine values must be the same.