第六章第三十六题(几何：正多边形的面积)(Geometry: area of a regular polygon)

*6.36（几何：正多边形的面积）正多边形是一个n条边的多边形，它的每条边的长度都相等，而且所有角的角度也相等（即多边形既是等边又等角的）。计算正多边形面积的公式是：

使用下面的方法头编写方法，返回正多边形的面积：

public static double area(int n, double side)

编写一个main方法，提示用户输入边的个数以及正多边形的边长，然后显示它的面积。

下面是一个运行示例：

Enter the number of sides: 5

Enter the side:6.5

The area of the polygon is 72.690170

*6.36(Geometry: area of a regular polygon) A regular polygon is an n-sided polygon in which all sides are of the same length and all angles have the same degree (i.e., the polygon is both equilateral and equiangular). The formula for computing the area of a regular polygon is

Write a method that returns the area of a regular polygon using the following header:

public static double area(int n, double side)

Write a main method that prompts the user to enter the number of sides and the side of a regular polygon and displays its area.

Here is a sample run:

Enter the number of sides: 5

Enter the side:6.5

The area of the polygon is 72.690170

下面是参考答案代码:

import java.util.*;

public class AreaOfRegularPolygonQuestion36 {
  public static void main(String[] args) {
    double area, side;
    int numberOfSide;

    Scanner inputScanner = new Scanner(System.in);
    System.out.print("Enter the number of sides: ");
    numberOfSide = inputScanner.nextInt();
    
    System.out.print("Enter the side: ");
    side = inputScanner.nextDouble();
    
    area = area(numberOfSide, side);
    System.out.printf("The area of the polygon is %f", area);
    
    inputScanner.close();
  }
  public static double area(int n, double side) {
    double area = (n * Math.pow(side, 2)) / (4 * Math.tan(Math.PI / n));
    return area;
  }
}

运行效果：

注：编写程序要养成良好习惯
1.文件名要用英文，具体一点
2.注释要英文
3.变量命名要具体，不要抽象（如:a,b,c等等），形式要驼峰化
4.整体书写风格要统一（不要这里是驼峰，那里是下划线，这里的逻辑段落空三行，那里相同的逻辑段落空5行等等）
5.普通变量，方法名要小驼峰，类名要大驼峰，常量要使用全部大写加上下划线命名法
6.要学习相应的代码编辑器的一些常用快捷键，如：快速对齐等等