Answer:
The range of y is ![[-\dfrac{5}{2},\dfrac{1}{2}]](https://tex.z-dn.net/?f=%5B-%5Cdfrac%7B5%7D%7B2%7D%2C%5Cdfrac%7B1%7D%7B2%7D%5D)
Step-by-step explanation:
Given: 
It is cosine function of trigonometry.
We need to find the range of given function. The value of y shows range of function.
y is depends on cosine function.
As we know cosine max/min value is fixed.
y is max when cosine max.
y is min when cosine is min.
Maximum value of cosine = 1

Minimum value of cosine = -1

Range of y: [min,max]
Range: ![[-\dfrac{5}{2},\dfrac{1}{2}]](https://tex.z-dn.net/?f=%5B-%5Cdfrac%7B5%7D%7B2%7D%2C%5Cdfrac%7B1%7D%7B2%7D%5D)
Hence, The range of y is ![[-\dfrac{5}{2},\dfrac{1}{2}]](https://tex.z-dn.net/?f=%5B-%5Cdfrac%7B5%7D%7B2%7D%2C%5Cdfrac%7B1%7D%7B2%7D%5D)