An interactive applet and associated web page that demonstrate how to construct a tangent to a cicrle at a given point on the circle, using compass and straightedge. It starts with the given circle and point, and in an animation that can run without stopping or single stepped, shows how to construct the tangent line through that point. The text on the page contains written step-by-step instructions that can be printed.

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.