Trikampis

#include <cmath>
#include <fstream>
#include <iostream>

using namespace std;

void atstumas (double x1, double y1, double x2, double y2, double &e);
void plotas (double atkarpa1, double atkarpa2, double atkarpa3, double &s);

int main (){
ifstream duom("duomenys.txt");
ofstream rez("rezultatai.txt");
double ax, ay, bx, by, cx, cy, xt, yt, AB, BC, AC, AD, BD, DC, ABC, DBC, DAC, DAB, plotsum;
duom>>ax>>ay>>bx>>by>>cx>>cy>>xt>>yt;
atstumas (ax, ay, bx, by, AB);
atstumas (ax, ay, cx, cy, AC);
atstumas (bx, by, cx, cy, BC);
atstumas (bx, by, xt, yt, BD);
atstumas (xt, yt, cx, cy, DC);
atstumas (ax, ay, xt, yt, AD);
plotas (AB, AC, BC, ABC);
plotas (AD, AB, BD, DAB);
plotas (AD, DC, AC, DAC);
plotas (BD, BC, DC, DBC);
plotsum=DAB+DAC+DBC;
if (ABC == plotsum) rez<<"Taskas yra trikampio viduje"<<endl;
else rez<<"Taskas yra trikampio isoreje"<<endl;

}
void atstumas (double x1, double y1, double x2, double y2, double &e){
    e=sqrt(((x2-x1)*(x2-x1))+((y2-y1)*(y2-y1)));
}
void plotas (double atkarpa1, double atkarpa2, double atkarpa3, double &s){
    double p;
    p=(atkarpa1+atkarpa2+atkarpa3)/2;
    s=sqrt(p*(p-atkarpa1)*(p-atkarpa2)*(p-atkarpa3));
}