This tutorial demonstrates the Circumcenter Theorem: The circumcenter of a triangle is equidistant from the vertices of the triangle. You will construct the circumcenter using only the "circle with fixed radius" and "line" tools.

 

The circumcenter is defined as the intersection of the perpendicular bisectors of all three sides of the triangle. To find it, proceed as follows: 

  • Make fixed circles around each point. Each time you create a fixed circle, the dialog box comes up. Put the same number in the Radius field for each circle (for instance, I chose 5).
  • Each pair of circle intersects in two points. Draw a line through these two points. Do this for every pair of circles (you should draw three lines).
  • The intersection of the three lines should be U.
  • Click the Fixed Circle tool. Make U the center, and click somewhere near A.
  • In the “Edit Circle” dialog box, select “Set Size…” The dialog disappears.
  • Click on U and then click on A.
  • The “Well Done!” screen should appear.


This ends the tutorial for fixed circles.