#### Answer

$\cos(-4x)$ and $-\cos(4x)$ are negatives of each other.

#### Work Step by Step

The answer to Exercise 87 is $y=-\cos(4x)$.
This means that there is a negative relationship between this answer and $y=\cos(4x)$, making $\cos(-4x)=-\cos(4x)$ an even-odd identity.