Final answer:
The midline of the wave function is located at y = 2.0.
Step-by-step explanation:
The midline of a wave function represents the average position of the wave over time. In this case, the peak of the wave function is at (1.2, 5.5) and the amplitude is 3.5. Since the amplitude represents the distance from the peak to the midline, we can calculate the midline by subtracting the amplitude from the y-coordinate of the peak.
Midline = y-coordinate of peak - amplitude
Midline = 5.5 - 3.5
Midline = 2.0
Therefore, the midline is located at y = 2.0.