#include <stdio.h>
#define pi 3.1415926
int main()
{
double a;
scanf("%lf", &a);
printf("正方形面积:%lf\n", a * a);
printf("内接圆面积:%lf\n", pi * a * a / 4);
printf("外接圆面积:%lf\n", pi * a * a / 2);
return 0;
}
原文：https://www.cnblogs.com/bobotongxue/p/12290647.html