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

Topic:
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.