Perpendicular Bisector

$\begin{figure}\begin{center}\BoxedEPSF{perpendicular_bisectors.epsf scaled 1000}\end{center}\end{figure}$

The perpendicular bisectors of a Triangle $\Delta A_1A_2A_3$ are lines passing through the Midpoint of each side which are Perpendicular to the given side. A Triangle's three perpendicular bisectors meet at a point known as the Circumcenter (which is also the center of the Triangle's Circumcircle).