Exploring Symmetry in Geometry Lessons

1. Symmetry 8-11 Course 2 Warm Up Problem of the Day Lesson Presentation

2. Symmetry 8-11 Course 2 Warm Up 1.Give the coordinates of triangle ABC with vertices (7, 2), (1, 2), (4, –5) reflected across the y-axis. 2. Give the coordinates of triangle ABC translated 3 units left and 2 units down. (–7, 2), (–1, 2), (–4, –5) (4, 0), (–2, 0), (1, –7)

3. Symmetry 8-11 Course 2 Problem of the Day There are some capital letters in our alphabet that have both horizontal and vertical lines of symmetry. Which of the 50 states can you spell using only letters from that group? OHIO

4. Symmetry 8-11 Course 2 Learn to identify symmetry in figures.

5. Symmetry 8-11 Course 2 Insert Lesson Title Here Vocabulary line symmetry line of symmetry asymmetry rotational symmetry center of rotation

6. Symmetry 8-11 Course 2 When you can draw a line through a plane figure so that the two halves are mirror images of each other, the figure has line symmetry, or is symmetrical. The line along which the figure is divided is called the line of symmetry. When a figure is not symmetrical then it has asymmetry, or is asymmetrical

7. Symmetry 8-11 Course 2 Additional Example 1: Identifying Line Symmetry Decide whether each of the figures has line symmetry. If it does, draw all the lines of symmetry. A. B. no line of symmetry 1 line of symmetry

8. Symmetry 8-11 Course 2 Insert Lesson Title Here Check It Out: Example 1 Decide whether each figure has line symmetry. If it does, draw all lines of symmetry. A. B. 1 line of symmetry no line of symmetry

9. Symmetry 8-11 Course 2 Additional Example 2: Finding Lines of Symmetry Find all the lines of symmetry in each figure. A. There are two lines of symmetry. B. There are no lines of symmetry.

10. Symmetry 8-11 Course 2 Insert Lesson Title Here Check It Out: Example 2 Find all the lines of symmetry in each figure. There are no lines of symmetry. A. B. There is 1 line of symmetry.

11. Symmetry 8-11 Course 2 A figure has rotational symmetry if, when it is rotated less than 360° around a central point, it coincides with itself. The central point is called the center of rotation.

12. Symmetry 8-11 Course 2 Additional Example 3A: Identifying Rotational Symmetry Tell how many times each figure will show rotational symmetry within one full rotation. Draw lines from the center of the figure out through identical places in the figure. Count the number of lines drawn. The figure will show rotational symmetry 4 times within a 360° rotation.

13. Symmetry 8-11 Course 2 Additional Example 3B: Identifying Rotational Symmetry Tell how many times each figure will show rotational symmetry with one full rotation. Draw lines from the center of the figure out through identical places in the figure. Count the number of lines drawn. The figure will show rotational symmetry 3 times within a 360° rotation.

14. Symmetry 8-11 Course 2 Insert Lesson Title Here Check It Out: Example 3A Tell how many times each figure will show rotational symmetry within one full rotation. Draw lines from the center of the figure out through identical places in the figure. Count the number of lines drawn. The figure will show rotational symmetry 4 times within a 360° rotation.

15. Symmetry 8-11 Course 2 Insert Lesson Title Here Check It Out: Example 3B Tell how many times each figure will show rotational symmetry within one full rotation. Draw lines from the center of the figure out through identical places in the figure. Count the number of lines drawn. The figure will show rotational symmetry 4 times within a 360° rotation.

16. Symmetry 8-11 Course 2 Insert Lesson Title Here Lesson Quiz Decide whether each figure has line symmetry. If it does, draw all the lines of symmetry. 1. 2. 3. Tell how many times the figure will have rotational symmetry with one full rotation. 8