The vertical shift of the graph moves the function up three units. Since there are no other major shifts to the height of the graph, the midline has an equation of y = 3.
the maximum value of sin(x-π) is 1, the minimum is -1, so the maximum value for the function y = 2sin(x - π) + 3 is 2*1+3=5, the minimum is -2+3=1, half way between 5 and 1 is 3, so y=3 is the midline.
