题目:给定圆的半径r, 求圆的面积。
C++:
nclude<iostream>
#include<cmath>
using namespace std;
int main(){
int r;
cin>>r;
double s;
double PI=atan(1.0)*4;
s=PI*r*r;
printf("%.7lf",s);
return 0;
}
Java:
package UKingW;
import java.util.Scanner;
public class Begin3 {
public static void main(String[] args) {
final double p=3.14159265358979323;
Scanner in=new Scanner(System.in);
int r=in.nextInt();
in.close();
System.out.printf("%.7f", p*r*r);
}
}