'A line perpendicular to the given plane.
Parameters
pt: Point3D
Returns
Line3D
Examples
>>> from sympy import Plane, Point3D, Line3D
>>> a = Plane(Point3D(1,4,6), normal_vector=(2, 4, 6))
>>> a.perpendicular_line(Point3D(9, 8, 7))
Line3D(Point3D(9, 8, 7), Point3D(11, 12, 13))'

def perpendicular_line(self, pt):

    a = self.normal_vector
    return Line3D(pt, direction_ratio=a)
