Relationship between Arc length, Area of Sector, Radius and Angle (in degrees)

Area, Circle
Original creation of this applet goes to Jennifer Silverman and subsequent changes by Tim Brzezinski (derived from this worksheet.) Interact with this applet for a few minutes, then answer the question that follows.
Is there any relationship among the arc length, sector area , its angle subtended at the centre of the circle (in degrees), and the radius of the circle? If so, describe.