double-click inside applet to toggle grid display.
click on numerical "Area=..."/"Length=..." display to double that value.
drag with mouse to change radius of arc or enter new value in edit-field.
press keys "q","h" or "f" for setting quarter-,half- and full-circles.
press "R" or "r" to rotate clock- or counterclockwise.
to the linear function calculations
(this page has been updated on October-28-2006)