A figure does not have to be a regular polygon to tessellate. Every triangle and every quadrilateral tessellates, as the figures below show.

A tessellation consists of a repeating triangle, alternating pointing up and pointing down. Each angle of the triangle appears twice at each vertex. A tessellation consists of a repeating quadrilateral, with each angle appearing at each vertex.

Every tessellation has at least one type of symmetry. The tessellation with regular hexagons below has reflectional symmetry in each of the blue lines. It has rotational symmetry centered at each of the red points. The tessellation also has translational symmetry and glide reflectional symmetry, as shown below.

A tessellation consists of a repeating hexagon, with three blue diagonals and three lines connecting midpoints of opposite sides. Red points are at each vertex, each midpoint, and the center.

The tessellation of repeating hexagons shows a slide to the right from a hexagon in one column to the hexagon two columns away.

In translational symmetry, a translation maps the tessellation onto itself.

The tessellation of repeating hexagons shows a hexagon sliding up one whole hexagon, and then reflected to two columns to the left across a vertical line through the center of the column to the left.

In glide reflectional symmetry, a glide reflection maps the tessellation onto itself.


End ofPage 597

Table of Contents

Prentice Hall Geometry Chapter 1 Tools of Geometry Chapter 2 Reasoning and Proof Chapter 3 Parallel and Perpendicular Lines Chapter 4 Congruent Triangles Chapter 5 Relationships Within Triangles Chapter 6 Polygons and Quadrilaterals Chapter 7 Similarity Chapter 8 Right Triangles and Trigonometry Chapter 9 Transformations Chapter 10 Area Chapter 11 Surface Area and Volume Chapter 12 Circles Skills Handbook Reference Visual Glossary Selected Answers Index Acknowledgments