#include <iostream> using namespace std; const double PI = 3.14159; //定义圆周率(π) double r; //定义r int main() { cin >> r;//输入r printf("%.4lf ", r * 2.0); //直径 printf("%.4lf ", 2.0 * r * PI); //周长 printf("%.4lf ", r * r * PI); //面积 return 0; }
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