1. Symmetry: A Visual Presentation
A PowerPoint Presentation created by Mrs. Gamache using the collection of web pages created by the Adrian Bruce and students of 6B
Geometry, Unit 7, Lesson 4
       

2. Line Symmetry
Shape has line symmetry when one half of it is the mirror image of the other half.
Symmetry exists all around us.
        How would you define the term 'line symmetry'?         Why might some people see line symmetry as a thing of beauty?

3. Is a butterfly symmetrical?

4. At the beach there are a variety of shells with line symmetry.

5. Under the sea there are also many symmetrical objects such as these crabs and this starfish.
This type of symmetry is also called reflectional symmetry as the two parts reflect/match along each side of a dividing line ( or axis ).

6. Animals that have Line Symmetry
Here are a few more great examples of mirror image in the animal kingdom.

7. THESE MASKS HAVE SYMMETRY
These masks have a line of symmetry from the forehead to the chin.  
The human face also has a line of symmetry in the same place.

8. REFLECTION IN WATER
If an object is reflected in water it is considered to have line symmetry along the waterline.

9. The Taj Mahal
In this view of the building there is a line of symmetry through the centre of the tomb from top to bottom. It was completed in 1630 by the Indian ruler Shahs Jahan as a tomb for his favourite wife Mumtaz Mahal who died as a result of giving birth to their 14th child.
To build this tomb it took workers, 20 years (Encarta 97) and it is rumoured that they used elephants to transport the materials.
Symmetry exists in architecture all around the world.  The best known example of this is the Taj Mahal.

10. This photograph shows 2 lines of symmetry
This photograph shows 2 lines of symmetry. One vertical, the other along the waterline.
(Notice how the prayer towers, called minarets, are reflected in the water and side to side).

11. an equilateral triangle has 3 lines of symmetry.

12. a square has 4 lines of symmetry.

13. a regular pentagon has 5 lines of symmetry.

14. a regular hexagon has 6 lines of symmetry .

15. a regular octagon has 8 lines of symmetry.
Is there a pattern here?
            How could you prove that a square really does have 4 lines of symmetry and not 2.             A rectangle has 4 lines of symmetry. True or False? How could you prove it?             What pattern can you see emerging on this page?

16. The Alphabet
In the alphabet, what capital letters have vertical symmetry? Horizontal symmetry? Both?
Vertical: AHIMOTUVWXY
Horizontal: BCDEHIKOX
Both: HIOX

17. Definition
Rotational symmetry any figure that can rotate 180° or less that maps the figure onto itself.
Example:
180°

18. State which objects have rotational symmetry60 60 60

19. Work Together!
With a partner, find examples of symmetrical objects in the classroom. For each object that you find, sketch it and list its symmetries. This is timed.
Points:
Reflectional Symmetry = 1 point
Rotational Symmetry of 180° = 2 points
Rotational Symmetry other than 180° = 3 points