An interactive applet and associated web page that demonstrate the diameter of a circle. The applet shows a circle and a diameter line, the ends of which can be dragged to show that the diameter passes through the center and has a constant length regardless of where on the circle it is drawn. The web page has the circle-related formulae.

See also entries for radius and circumference

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.