Important Facts about 3-Space: 

(More may be added soon)

• Given two points A and B, the set of points P equidistant from A and B form a plane through the midpoint of AB and perpendicular to line AB.  We call this the perpendicular bisecting plane of AB.

• Given a plane p and a point A, the reflection of A in p is the point A' so that p is the perpendicular bisecting plane of AA'.  In other words, AA' is perpendicular to p and intersects AA' at its midpoint.  Reflection in p is an isometry of 3-space.

• A figure S in space has p as a plane of symmetry if the reflection of S in p is again S.