GeoGebra 4 - Arc Length and Radian Measure

Directions: Click and drag the slider points to change the angle and the radius.

Sorry, the GeoGebra Applet could not be started. Please make sure that Java 1.4.2 (or later) is installed and activated. (click here to install Java now)

Now go back and find out how to make this and why it works!
 

LFS, Created with GeoGebra