What is a radian?

Do you know what a radian is? Use the drag bar to change the angle of theta or the number or radians. Do you notice any relationships between the length of your arc and the length of your radius?

This is a Java Applet created using GeoGebra from www.geogebra.org - it looks like you don't have Java installed, please go to www.java.com

A radian is the measure of the central angle subtended by an arc equal in length to the radius of a circle.

So how many radian's do you need to go completely around the circle?

Breanna Allred, November 19, 2012, Created with GeoGebra