[C++] 삼각형 넓이 구하기

#include <iostream>
#include <cmath>

using namespace std;
double triangle(double a, double b, double c, double d, double e, double f);

int main(void)
{
double a = 0, b = 0;
double c = 0, d = 0;
double e = 0, f = 0;
cin >> a; cin >> b;
cin >> c; cin >> d;
cin >> e; cin >> f;
cout << "(" << a << "," << b << "), (" << c << "," << d << "), (" << e << "," << f<<")가 이루는 삼각형 면적은?\n" << endl;
cout << "삼각형의 면적 : " << double(abs(triangle(a, b, c, d, e, f))/2);
return 0;
}

double triangle(double a, double b, double c, double d, double e, double f)
{
double area = (a*d + c*f + e*b-b*c-e*d-a*f);
return area;
}