An interactive applet and associated web page that show the definition and properties of a square when applied in coordinate geometry. The applet has a square, and the user can drag any vertex to re-size it. It shows how to calculate the side lengths and diagonal length given the vertex coordinates.

The grid and coordinates can be turned on and off. The applet can be printed as it appears on the screen to make handouts.

The web page has a full definition of a square when the coordinates of the points defining it are known, and has links to other pages relating to coordinate geometry.

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.