Question

用C++语言写一个程序，输入一个圆的半径，分别求其面积和周长

Answer 1

#...
int r,b,d
sin<<"输入圆的半径“<<r<<endl;
b=π*r^2;
d=π*2*r;
cout<<"面积为“<<b<<endl;
cout<<”周长wei"<<d<<endl;

Answer 2

#include <iostream>
using namespace std;
const double PI = 3.141592654;
int main()
{
double r;
cin >> r;
cout << "半径为：" << r << endl;
cout << "周长为：" << 2*PI*r << endl;
cout << "面积为：" << PI*r*r << endl;
return 0;
}

Answer 3

#include<iostream>
using namespace std;
#define pi 3.14

int main()
{
double r=0;
double area=0,length=0;
cout<<"输入半径："<<endl;
cin>>r;
area = pi*r*r;
length = 2*pi*r;
cout<<"面积："<<area<<endl;
cout<<"周长："<<length<<endl;
return 0;
}