1. EQ: How can I identify symmetry in figures? Do Now 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. HWK: TXBK p 496 #1-18even & p 141 #1-44 even (–7, 2), (–1, 2), (–4, –5) (4, 0), (–2, 0), (1, –7) Course 2 8-11 Symmetry

2. Vocabulary line symmetry – a figure has line symmetry if one-half is a mirror image of the other half. line of symmetry - imaginary “mirror” in line of symmetry Asymmetry – not identical on either side of a central line Insert Lesson Title Here Course 2 8-11 Symmetry

3. rotational symmetry – a figure has rotational symmetry if it can be rotated less than 360 0 around a central point and coincide with the original figure. center of rotation – the point about which a figure is rotated

4. 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 Course 2 8-11 Symmetry

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

6. Check It Out: Example 1 Decide whether each figure has line symmetry. If it does, draw all lines of symmetry. Insert Lesson Title Here A.B. 1 line of symmetryno line of symmetry Course 2 8-11 Symmetry

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

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

9. 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. Course 2 8-11 Symmetry

10. 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. Course 2 8-11 Symmetry

11. Tell how many times each figure will show rotational symmetry with one full rotation. Additional Example 3B: Identifying Rotational Symmetry 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. Course 2 8-11 Symmetry

12. Check It Out: Example 3A Tell how many times each figure will show rotational symmetry within one full rotation. Insert Lesson Title Here 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. Course 2 8-11 Symmetry

13. Check It Out: Example 3B Insert Lesson Title Here 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. Course 2 8-11 Symmetry

14. Construction List steps to copy a segment: List steps to copy an angel:

15. Construction List steps to bisect a segment: List steps to bisect an angle:

16. Construction List steps to construct perpendicular lines: List steps to construct perpendicular bisector:

17. Construction List steps to construct parallel lines

18. TOTD Decide whether each figure has line symmetry. If it does, draw all the lines of symmetry. Insert Lesson Title Here 1.2. 3. Tell how many times the figure will have rotational symmetry with one full rotation. 8 Course 2 8-11 Symmetry