7-11 计算正五边形的面积和周长 (10 分)

题意

正确代码

import java.text.DecimalFormat;
import java.util.Scanner;

class Main {
	public static void main(String[] args) {
   Scanner sc =new Scanner(System.in); 
  double a=sc.nextDouble();
  double s=a*a*Math.sqrt(25.0+10.0*Math.sqrt(5.0))/4.0;
  double c=a*5;

  DecimalFormat df=new DecimalFormat("#.####");
  System.out.printf(df.format(s));
 
System.out.println();
	  System.out.printf(df.format(c));
    sc.close();
   
}
}

错误代码

错误原因：不会....

import java.util.Scanner;

class Main {
	public static void main(String[] args) {
   Scanner sc =new Scanner(System.in); 
  double a=sc.nextDouble();
  double s=a*a*Math.sqrt(25.0+10.0*Math.sqrt(5.0))/4.0;
  double c=a*5;

  System.out.printf("%.4f\n",s);
 

	  System.out.printf("%.4f\n",c);
    sc.close();
   
}
}