c++ 已知到三点的距离，求当前点坐标

QQ:609162385

QPoint  MainWindow::calcPhonePosition(double x1, double y1, double d1,
                                      double x2, double y2, double d2,
                                      double x3, double y3, double d3) {
    QPoint d;
    double a11 = 2 * (x1 - x3);
    double a12 = 2 * (y1 - y3);
    double b1 = pow(x1, 2) - pow(x3, 2)
            + pow(y1, 2) - pow(y3, 2)
            + pow(d3, 2) - pow(d1, 2);
    double a21 = 2 * (x2 - x3);
    double a22 = 2 * (y2 - y3);
    double b2 = pow(x2, 2) - pow(x3, 2)
            + pow(y2, 2) - pow(y3, 2)
            + pow(d3, 2) - pow(d2, 2);
    d.setX((b1 * a22 - a12 * b2) / (a11 * a22 - a12 * a21));
    d.setY((a11 * b2 - b1 * a21) / (a11 * a22 - a12 * a21));

    return d;
}