控制台程序
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace test3_3
{
class Program
{
static void Main(string[] args)
{
const double PI = 3.1415926;
Console.WriteLine("请输入圆的半径:");
double r = int.Parse(Console.ReadLine());
double area = r * r * PI;
Console.WriteLine("圆的面积是{0}",area);
Console.ReadLine();
}
}
}