An interactive applet and associated web page that shows that side-side-angle is not enough to prove congruence, because two triangles can meet the condition. The applet shows two triangles, one of which can flip between the two possible configurations that both meet the SSA criteria, showing it is insufficient.

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.