在一个正n边形中，所有的边长都相同，且所有的度数都相同。设计一个RegularPolygon的类，要求可以计算这个正多边形的面积和周长。要求画出该类的UML图并实现这个类。编写一个测试程序，分别测试正三角形、正五边形、正六边形的面积和周长。-In an n-gon, all sides are the same length, and all have the same degree. RegularPolygon design a class that requires regular polygon can calculate the area and perimeter. Requirements draw UML class diagram and implement this class. Write a test program, were tested equilateral triangle, pentagon, hexagon area and perimeter.