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

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
• 参考代码：

package chapter06;

import java.util.Scanner;

public class Code_36 {
    
    
    public static void main(String[] args) {
    
    
        Scanner inputScanner = new Scanner(System.in);
        System.out.print("Enter the number of sides: ");
        int numberOfSide = inputScanner.nextInt();
        System.out.print("Enter the side: ");
        double side = inputScanner.nextDouble();
        double area = area(numberOfSide, side);
        System.out.printf("The area of the polygon is %f", area);
    }
    public static double area(int n, double side) {
    
    
        double area = (n * Math.pow(side, 2)) / (4 * Math.tan(Math.PI / n));
        return area;
    }
}

• 结果显示：

Enter the number of sides: 5
Enter the side: 6.5
The area of the polygon is 72.690170
Process finished with exit code 0