Determine the midline of the following function: \[ y=-\sin \left(\frac{1}{2} x\right)-8 \]

Step 1 ：Determine the midline of the following function: \(y=-\sin \left(\frac{1}{2} x\right)-8\)

Step 2 ：The midline of a sinusoidal function is the horizontal line that cuts the graph in half. It is given by the constant term in the function.

Step 3 ：In this case, the constant term is -8, so the midline of the function is y = -8.

Step 4 ：Final Answer: The midline of the function is \(\boxed{y = -8}\)