We have the function
F(x) = 1.5 + cos (x)
Note that the minimum value the cos is -1
Therefore, the lowest point can be calculated by substituting cos(x) = -1
f(-1) = 1.5 + (-1)
= 1.5 - 1
= 0.5
Lowest point is 0.5
The maximum value of cos is 1
So, the highest point is
f(1) = 1.5 + 1
= 2.5
The highest point is 2.5
Midline = Highest point + lowest point / 2
Midline = 2.5 + 0.5 / 2
Midline = 3 / 2
Midline = 1.5
F(x) = 1.5
The answer is 1.5