import math
def GetGeographicalRadians(shape):

    radian = math.atan2(shape.lastpoint.y - shape.firstpoint.y,
                        shape.lastpoint.x - shape.firstpoint.x)
    if (radian<0):
        radian = (radian+math.pi)*(-1)+math.pi
    else:
        radian=(radian-math.pi)*(-1)+math.pi
    return radian