Write a class named Dodecagon whose objects represent regular dodecagons (12-sided polygons). Your class should implement the Shape interface defined in this chapter. A Dodecagon object is defined by its side length as passed to its constructor. The common formulas for the area and perimeter of a regular dodecagon are based on its circumradius, which is the radius of the smallest circle that would fully contain the dodecagon. We suggest reading about these formulas on a web site such as Wikipedia or Wolfram MathWorld.