#include <stdio.h>
#include <math.h>
int main(void)
{
double a = 3.0;
double b = 6.0;
double c = 7.0;
double s; // semi (half) perimeter
double area;
s = (a + b + c) / 2.0;
area = s * (s - a) * (s - b) * (s - c);
area = sqrt(area);
printf("area = %lf", area);
return 0;
}
/*
run:
area = 8.944272
*/