Reflection

Definition:  Given a line L in the plane, the reflection of the point P across the line L is the point P' such that the following properties of P and P' are satisfied:

  1.  If P is not on L, then PP' is perpendicular to L and P and P' are equidistant from L.
  2.  If P is on the line L then P=P'.

 

Example:

 The point P' is the reflection of point P about the line L.