The middle of a line segment is its midpoint. To find the midpoint of a line segment, you just calculate the averages of the coordinates — easy as pie.
The midpoint, M, of a segment with endpoints (x1,y1) and (x2,y2) is
If you want to know the midpoint of the segment with endpoints (–4,–1) and (2,5), then plug the numbers into the midpoint formula, and you get a midpoint of (–1,2):
See how this segment looks in graph form in the following figure.
