To find the length of a line segment, given the coordinates of its endpoints, we can use two methods.
Find the length of the line segment AC whose endpoints are at:
A(-5, -3) and C(3, -3).
Plot the points and count the squares.
This is a good method if you have time to do it and paper and pencil to hand!
AC is 8 units long. Just write 8
If you don't have the time to plot the coordinates, this method is the best!
Subtract the relevant coordinates.
The x-coordinates of the endpoints of vertical lines will be the same.
The y-coordinates of the endpoints of horizontal lines will be the same.
A is at (-5, -3) and C is at (3, -3).
The line AC is horizontal because the y-coordinates are both -3.
Subtract the x-coordinates: -5 - 3 = -8 or 3 - -5 = 8.
Ignore the sign: -8 or 8 means a length of 8 units. Just write 8.
For vertical lines, we would subtract the y-coordinates.
Let's give it a try in some questions now.