An interactive applet and associated web page that demonstrate the properties of the circumcircle of a triangle.

The applet shows a triangle where the user can drag the vertices to reshape it. The circumcircle (the circle that passes through all vertices) is continuously updated as the triangle is resized. The center of the circle (circumcenter) is shown along with the three side bisectors that define it.

Applet can be enlarged to full screen size for use with a classroom projector. After use in the classroom, student can access it again from any web browser at home or in the library with no login required.

This resource is a component of the Math Open Reference Interactive Geometry textbook project at http://www.mathopenref.com.