Answer:
y=3 is the midline of the given cosine function.
Explanation:
The midline is a horizontal axis that acts as a reference line about which a graph of a periodic function oscillates.
It is the average of maximum and minimum values of the function.
The maximum value of the cosine function is y=4
The minimum value of the cosine function is y=2
∴ The midline of the cosine function = (4+2)/2 = 3
Hence, y=3 is the midline of the given cosine function.
Refer attachment for the graph.