void PndTpcLheTrackCuts::Circle3pnts(Double_t x[],Double_t y[], Double_t r[]) {
// calc center and R of circle from 3 points

Double_t m_a = (y[1] - y[0]) / (x[1] - x[0]);
Double_t m_b = (y[2] - y[1]) / (x[2] - x[1]);

if (m_a != m_b) {
Double_t x_c = .5*(m_a* m_b*(y[0] - y[2]) +
m_b*(x[0] + x[1]) -
m_a*(x[1] + x[2])) / (m_b - m_a);

Double_t y_c = - (x_c - .5*(x[0] + x[1])) / m_a +
.5*(y[0] + y[1]);

Double_t dely = y_c - y[0];
Double_t delx = x_c - x[0];
Double_t rad =TMath::Sqrt(delx*delx + dely*dely);

r[0] = x_c;
r[1] = y_c;
r[2] = rad;
}

}

void PndTpcLheTrackCuts::Circle3pnts(Double_t x[],Double_t y[], Double_t r[]) {
// calc center and R of circle from 3 points

Double_t x_c = 0., y_c = 0.;

if ( (y[1] - y[0])*(x[2] - x[1]) == (x[1] - x[0])*(y[2] - y[1]))
{
cout << " -W- PndTpcLheTrackCuts::Circle3pnts: The points lay on a straight line" << endl;
x_c = 10000.;
y_c = 10000.;
}
else
{
if ((x[1] - x[0])!=0 && (x[2] - x[1])!=0)
{
Double_t m_a= (y[1] - y[0]) / (x[1] - x[0]);
Double_t m_b = (y[2] - y[1]) / (x[2] - x[1]);

x_c = .5*(m_a* m_b*(y[0] - y[2]) +
m_b*(x[0] + x[1]) -
m_a*(x[1] + x[2])) / (m_b - m_a);
y_c = - (x_c - .5*(x[0] + x[1])) / m_a +
.5*(y[0] + y[1]);
}
else
{
Double_t m_a = (x[1] - x[0]) / (y[1] - y[0]);
Double_t m_b = (x[2] - x[1]) / (y[2] - y[1]);

y_c = .5*(m_a* m_b*(x[0] - x[2]) +
m_b*(y[0] + y[1]) -
m_a*(x[1] + x[2])) / (m_b - m_a);
x_c = - (y_c - .5*(y[0] + y[1])) / m_a +
.5*(x[0] + x[1]);
}

} // end of not collinear points condition

Double_t dely = y_c - y[0];
Double_t delx = x_c - x[0];

r[0] = x_c;
r[1] = y_c;
r[2] = TMath::Sqrt(delx*delx + dely*dely);
}