What is the midpoint of (5,4) and (5,-3)

Because the x-coordinates are identical (5), the line connecting the two given points is a vertical one whose lower y-coordinate is -3 and whose upper y-coordinate is 4. The midpoint of this line segment has the same x-coordinate (5) as do the two given points. The y-coordinate of the midpoint of this segment is the arithmetic mean (average) of 4 and -3:

y-coord. of midpoint = (4-3)/2 = 1/2.

Thus, the coordinates of the midpoint of this line segment are (5, 1/2).