public Line2 RotateZ(IVector3 rotationPt, double angleRad)
{
Line2 lineRot = new Line2();
lineRot.Point1 = Point1.RotateZ(rotationPt, angleRad);
lineRot.Point2 = Point2.RotateZ(rotationPt, angleRad);
lineRot.Col = Col;
return(lineRot);
}