作業二：圓的面積
```
#include
#define?PI?3.14
double?calculateArea?(int?radius);
int?main?()
{
int?cRadius?=0;
double?Area?=0.0;
printf("請輸入圓的半徑:\n");
scanf("%d",&cRadius);
Area=calculateArea(cRadius);
printf("圓的面積是:%f\n",Area);
return?0;
}
double?calculateArea?(int?radius)
{
double?result?=?PI*radius*radius;
return?result;
}
```
