Given a line segment with endpoints A and B, we must merely find a point on the perpendicular bisector of the line AB, then use the perpendicular line construction. To find the point on the perpendicular bisector, we must merely find a point that is equidistant from both A and B. We can do this with a compass by choosing a compass length greater than half the length AB, and then making an arc from A above the line AB. Then we make an arc from B having the same length.
<span>Since we used the same length for each arc, the intersection of the arcs, P, is equidistant from A and B. Now we simply use the perpendicular line construction for line AB and P, which is off the line. This line will be a perpendicular bisector. </span>
