An interactive applet and associated web page that demonstrate the concept of coplanar objects - those that lie in the same plane.

The applet presents two planes. In one plane there are two rectangles that can be dragged around and which lie in the same plane always. The other is a rectangle that can be dragged but always lies in a plane orthogonal to the first.

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.