2. Reflection and Rotation Symmetry

3. Reflection-Symmetric Figures A figure has symmetry if there is an isometry that maps the figure onto itself. If that isometry is a reflection, then the figure has reflection symmetry.

4. Activity 1: Lines of symmetry can cut through shapes that have reflection symmetry Draw in lines of symmetry for each: A C G none

5. Segment Theorem: Figures with reflection symmetry have their pre-images and images equal distances from the reflection mirror. 5 in 6 in 10 in 5 6 10

6. Circle Symmetry: How many lines of symmetry does a circle have?? Infinite!

7. Symmetric Figures Theorem: Any symmetric figure is congruent to its image

8. Rotation Symmetry: A figure has rotational symmetry if it’s congruent after a rotation of 180 degrees or less (greater than zero). Find the degrees of roation by dividing 360 by number of points. 360/3 = 120

9. Order of Rotational Symmetry The order of rotational symmetry that an object has is the number of times that it fits on to itself during a full rotation of 360 degrees.

10. What is the order of rotational symmetry of the shape below? Rotational Symmetry

11. 1 2 3 4 5 What is the order of rotational symmetry of the shape below? Order 5 Rotational Symmetry

12. What is the order of rotational symmetry of the shape below? Rotational Symmetry

13. 1 2 3 4 5 What is the order of rotational symmetry of the shape below? Order 6 Rotational Symmetry 6

14. Equilateral Triangle An equilateral triangle has rotational symmetry of order ? Regular Polygons

15. Equilateral Triangle An equilateral triangle has rotational symmetry of order ?

16. Equilateral Triangle An equilateral triangle has rotational symmetry of order ? 12 3 3

17. Square A square has rotational symmetry of order ? Square

18. A square has rotational symmetry of order ?

19. Square A square has rotational symmetry of order ? 12 3 4 4

20. Point Symmetry A figure also has point symmetry if it can be rotated 180 degrees. (If the figure looks the same upside down, then it has point symmetry.) 360/4 = 90 two rotation make 180

21. Examples: Name the type(s) of symmetry each figure has. Rotation of 120 reflection Rotation and point reflection