# How do you find the range of y = -2 cos 3x?

Range of $y = - 2 \cos 3 x$ is $\left[- 2 , + 2\right]$
Range of $\cos \left(\theta\right)$ for any Real $\theta$ (including $3 x$) is [-1,+1]
Multiplying this by $\left(- 2\right)$ just stretches the range to $\left[2 , - 2\right]$