面积area的算法:
area=√s(s-a)(s-b)(s-c)×s=(a+b+c)/2
#include <stdio.h>
#include <math.h>
float S(float a, float b, float c)
{
float s = (a + b + c) / 2;
return sqrt(s * (s - a) * (s - b) * (s - c));
}
void main()
{
printf("%.2f", S(3, 4, 5));
}