Chapter Twelve:  
Transformations

Geometry   Notes

Chapter  12

Section  12.1
Section  12.2
Section  12.3
Section  12.4
Section  12.5
Section  12.6
Section  12.7

Geometry Contents

Take notes on the following topics.

Section 12.1  Reflections

Vocabulary

Transformation (p. 634) A transformation is a change in the position, size, or shape of a geometric figure. The given figure is called the preimage and the resulting figure is called the image. A transformation maps a figure onto its image. Prime notation is sometimes used to identify image points. In the diagram, X′ (read "X prime") is the image of X.

Image (p. 634) An image is the result of a transformation of a point, line, or figure.

Isometry (p. 634) An isometry, also known as a congruence transformation, is a transformation in which an original figure and its image are congruent

Reflection (p. 635) A reflection in (or flip across) line r is a transformation such that if a point A is on line r, then the image of A is itself, and if a point B is not on line r, then its image B′ is the point such that r is the perpendicular of BB'.