#include <QCoreApplication>
#include <QLineF>
#include <QDebug>

int main(int argc, char *argv[])
{
    QLineF line1(QPointF(-8.588675134594819,7.828675134594815),QPointF(-8.433974596215569,7.673974596215563));
    QLineF line2(QPointF(-8.377350269189632,7.462649730810377),QPointF(-8.433974596215569,7.673974596215563));

    qreal angle  = line1.angle(line2);
    qreal angle2 = line1.angleTo(line2);

    qDebug() << angle <<  angle2;

    QCoreApplication app(argc, argv);

    return app.exec();
}