Explore this applet demonstrating the midpoint between two points.
What connections exist between the endpoints of a line segment and the midpoint?
The coordinates of the midpoint of a segment are half the sum of the x and y-coordinates of the end points.
The midpoint of a line segment is a point exactly halfway along the segment. That is, the distance from the midpoint to both of the endpoints is the same.
The midpoint of any two points has coordinates that are exactly halfway between the x-values and halfway between the y-values. This means we can find the average of the two given x-coordinates to find the x-coordinate of the midpoint, and likewise the average of the two y-coordinates will give us the y-coordinate of the midpoint.
So for points A \left(x_1,y_1\right) and B \left(x_2,y_2\right) the midpoint will be: M \left(\dfrac{x_1+x_2}{2}, \dfrac{y_1+y_2}{2} \right).
Think of it as averaging the x and y-values of the endpoints.
By convention, we work from left to right so the point with the lower x-value is generally considered to be the point corresponding to (x_1,y_1), but obviously if we went from right to left we should still end up with the same midpoint.
M is the midpoint of A(-8,-4) and B(2,8). Find the coordinates of M.
For points A \left(x_1,y_1\right) and B \left(x_2,y_2\right) the midpoint will be:
What if we are given the midpoint of a segment, and one endpoints points of the segment? How can we reverse our steps above to find the other endpoint?
If the midpoint of A(x,y) and B(16,7) is M(10,2), what are the coordinates of A?
To find the missing endpoint, equate the average of each x and y-value of the endpoints to each x and y-value of the given midpoint. Then solve for the unknown coordinates.