Rectifying Plane

The rectifying plane of a space curve L at a point M on L is the plane of the tangent and binormal to L at M. The envelope of the family of rectifying planes of L is a developable surface called the rectifying developable of L (seeRULEDSURFACE). On this surface, L is a geodesic. When the rectifying developable is developed on a plane, L becomes a straight line. In other words, L is “rectified”; this fact accounts for the term “rectifying plane.”