Функция отыскания длины сторон треугольника через вершины его координат.

#include <iostream>
#include <cmath>
using namespace std;
 
double length (double p1[2], double p2[2]);
int main ()
{
    int i;
    double A[2], B[2], C[2], a, b, c, P, S;
    cout <<"Enter the coordinats of point A"<<endl;
    for (i = 0; i < 2; i++)
        cin >> A[i];
    cout <<"Enter the coordinats of point B"<<endl;
    for (i = 0; i < 2; i++)
        cin >> B[i];
    cout <<"Enter the coordinats of point C"<<endl;
    for (i = 0; i < 2; i++)
        cin >> C[i];
    cout <<"The coordinats of point is A : ";
    for (i = 0; i < 2; i++)
        cout << A[i]<<" ";
    cout <<endl;
    cout <<"The coordinats of point is B : ";
    for (i = 0; i < 2; i++)
        cout << B[i]<<" ";
    cout <<endl;
    cout <<"The coordinats of point is C : ";
    for (i = 0; i < 2; i++)
        cout << C[i]<<" ";
    cout << endl;
    a = length( C, B );
    b = length( C, A );
    c = length( B, A );
    P = a + b + c;
    S = b * c * 0.5;
    cout <<"a is "<< a<<" b is "<< b << " c is "<< c<< endl;
    cout <<"Perimeter equals to "<< P <<endl <<"S = "<< S<< endl;
    system ("PAUSE");
    return 0;
}
double length(double p1[2], double p2[2])
{
    double length, s1, s2;
    s1 = p1[1] - p2[1];
    s2 = p1[2] - p2[2];
    length = sqrt(pow(s1,2) + pow(s2,2));
    return length;
}

double length(double p1[2], double p2[2])
{
 double length, s1, s2;
 s1 = p1[0] - p2[0];
 s2 = p1[1] - p2[1];
 length = sqrt(pow(s1,2) + pow(s2,2));
 return length;
}