三角形面积公式

#include<iostream>
#include<cmath>
#include<iomanip>
using namespace std;

int main()
{
    double a, b, c;

    cout << "please enter a, b and c:";
    cin >> a >> b >> c;
    
    if (a + b > c && b + c > a && c + a > b)//判断能否构成三角形
    {
        double s, area;

        s = 0.5 * (a + b + c);
        area = sqrt(s * (s-a) * (s-b) * (s-c));

        cout << setiosflags(ios::fixed) << setprecision(4);
        cout << "area = " << area << endl;
    }
    else cout << "it is not a trilateral!" << endl;
    while (1);
    return 0;
}