Answer:
The minimum value of y is -7
Explanation:
Given:

We are given a cosine function.
We need to find minimum value of function.

Here y is depends on cosine function.
y is minimum when cosine is minimum because y is directly proportional to cosine function.
Minimum value of cos x is -1
Therefore, For minium value of y

Minimum value of y


Hence, The minimum value of y is -7