Final answer:
The equation of the midline for the trigonometric function y=2cos(3x) + 2 is y=2, which represents the constant vertical shift from the center position of the cosine wave.
Step-by-step explanation:
The equation of the midline of a trigonometric function, such as y = 2cos(3x) + 2, can be found by identifying the constant term that vertically shifts the graph of the cosine function. Here, the cosine function is vertically shifted upwards by 2 units. Therefore, the midline is the horizontal line given by the equation y = 2, since this constant term represents the vertical displacement from the center position of the cosine wave.