#include <iostream>
#include <cmath>
using namespace std;
double TArea(double, double, double);
int main()
{
double a, b, c, alan;
cout << "Enter the sides of the triangle: ";
cin >> a >> b >> c;
alan = TArea(a, b, c);
cout << "The area of this triangle is "
<< alan << endl;
system("Pause");
return 0;
}
double TArea(double a, double b, double c)
{

if (a<0. || b<0. || c<0.) return 0.0;
if (a >= b+c) return 0.0;
if (b >= a+c) return 0.0;
if (c >= a+b) return 0.0;
double u, area;
u = 0.5*(a+b+c);
area = sqrt(u*(u-a)*(u-b)*(u-c));
return area;
}