9-4 Symmetry
Objective
To identify the type of symmetry in a figure
Lesson Vocabulary
- symmetry
- line symmetry
- reflectional symmetry
- line of symmetry
- rotational symmetry
- point symmetry
In the Solve It, you made a figure that is its own image under a transformation. In this lesson, you will learn to classify figures with this property.
Essential Understanding Some figures appear unchanged after a reflection across a line or a rotation about a point. Such figures are said to have symmetry.
A figure has symmetry if there is an isometry that maps the figure onto itself.
Take Note Key Concept: Types of Symmetry
A figure has line symmetry or reflectional symmetry if there is a reflection for which the figure is its own image. The line of reflection is called a line of symmetry. It divides the figure into congruent halves.
A figure has rotational symmetry if there is a rotation of
A figure with
A square, which has both
Table of Contents
- 6-1 The Polygon Angle-Sum Theorems
- 6-2 Properties of Parallelograms
- 6-3 Proving That a Quadrilateral Is a Parallelogram
- 6-4 Properties of Rhombuses, Rectangles, and Squares
- 6-5 Conditions for Rhombuses, Rectangles, and Squares
- 6-6 Trapezoids and Kites
- 6-7 Polygons in the Coordinate Plane
- 6-8 and 6-9 Coordinate Geometry and Coordinate Proofs