An interactive applet and associated web page that demonstrate equilateral triangles (all sides the same length). The applet presents an equilateral triangle where the user can drag any vertex. As the vertex is dragged, the others move automatically to keep the triangle equilateral. The angles are also updated continuously to show that the all interior angles are always congruent.

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.