An interactive applet and associated web page that demonstrate the area of a regular polygon. The applet presents a regular polygon where the user can drag any vertex to resize it, and change the number of sides from 3 to 99. As the changes are happening the area is recomputed and displayed continuously. The polygon is filled with a grid of unit squares so that the students can estimate the area. The on-screen calculation can be hidden until the estimates are done.

The text on the web page gives four different formulae for calculating the area, depending on the initial givens.

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.