Circumcenter
The three perpendicular bisectors are shown (in green) in the triangle.The intersection of the perpendicular bisectors is called the circumcenter.
The length segments from the circumcenter to the vertices is shown. As you change the shape of the triangle, what do you notice about the lengths of those segments?
Construct a circle centered at the circumcenter with the radius to a vertex. Drag the triangle. What do you notice about the circle?