An interactive applet and associated web page that demonstrate the concept of congruent triangles. Applets show that triangles are congruent if they are the same, rotated, or reflected. In each case, the user can drag one triangle and see how another triangle changes to remain congruent to it.

The web page describes all this and has links to other related pages.

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.