Triangle/Perpendicular bisector/Intersecting point/Fact/Proof
< Triangle < Perpendicular bisector < Intersecting point < Fact
Proof
The perpendicular bisector for the line segment between and consists, according to fact, exactly of those points of the plane that have to these points the same distance. Therefore, the intersecting point of the perpendicular bisector of and and the perpendicular bisector of and has the same distance to all three vertices. This gives the supplement, and also, that all three perpendicular bisectors meet in this point.