1. Pre-Algebra 5.8 Symmetry

2. Warm Up Identify each as a translation, rotation, reflection, or none of these. A. B. reflection rotation C. D. none of the thesetranslation

3. Learn to identify symmetry in figures.

4. line symmetry line of symmetry rotational symmetry Vocabulary

5. Nature provides beautiful examples of symmetry, such as the wings of a butterfly or petals of a flower. Symmetric objects have parts that are congruent. VOCAB: A figure has line symmetry if you can draw a line through it so the the two sides are mirror images of each other. The line is called line of symmetry.

6. If you fold a figure on the line of symmetry, the halves match exactly. Helpful Hint

7. A. Complete the figure. The dashed line is the line of symmetry. Example: Drawing Figures With Line Symmetry

8. B. Complete the figure. The dashed line is the line of symmetry. Example: Drawing Figures With Line Symmetry Continued

9. A. Complete the figure. The dashed line is the line of symmetry. Try This

10. B. Complete the figure. The dashed line is the line of symmetry. Try This

11. VOCAB: A figure has rotational symmetry if you can rotate the figure around some point so that it coincides with itself. The point is the center of rotation, and the amount of rotation must be less than one full turn or 360°. To find the amount of degrees you can turn the figure so that it looks the same, divide 360 by the number of “folds”. 6-fold rotational symmetry The figure coincides with itself every 60° (360/6) 8-fold rotational symmetry The figure coincides with itself every 45° (360/8)

12. A. 2-fold Complete the figure. The point is the center of rotation. The figure coincides with itself every 180° Example: Drawing Figures With Rotational Symmetry

13. B. 5-fold Complete the figure. The point is the center of rotation. The figure coincides with itself every 72° Example: Drawing Figures With Rotational Symmetry Continued

14. A. 8-fold Complete the figure. The point is the center of rotation. The figure coincides with itself every 45° Try This

15. B. 10-fold The figure coincides with itself every 36° Complete the figure. The point is the center of rotation. Try This

16. Does the figure described have symmetry? 1. a regular hexagon 2. the letter F 3. the letter M yes no yes Lesson Quiz: Part 1

17. 4. Complete the figure. The dashed line is the line of symmetry. Lesson Quiz Part 2