Symmetry:
A Visual Presentation
Symmetry
To be a line of symmetry, the
shape must have two halves
that match exactly.




When you trace a heart onto a
piece of folded paper,
and then cut it out, the two half
hearts make a whole heart.
  The two halves are symmetrical.
Line Symmetry
   Shape has line symmetry when one half
    of it is the mirror image of the other half.




   Symmetry exists all around us and many
    people see it as being a thing of
    beauty.
Is a butterfly symmetrical?
Line Symmetry exists in
nature but you may not
     have noticed.
At the  beach there are
a variety of shells with line
        symmetry.
Under the sea there are also
 many symmetrical objects
   such as these crabs



     and this starfish.
Animals that have Line
        Symmetry




Here are a few more great examples of
 mirror image in the animal kingdom.
Line Symmetry in the Alphabet

 Which letters have got lines of symmetry?


A B C D E F G H I
J K L M N O P Q R
S T U V W X Y Z
Lines of Symmetry all around us
Which of these road signs have got lines of
                symmetry?
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.
REFLECTION IN WATER


    If an object is
reflected in water it
  is considered to
have line symmetry
along the waterline.
The Taj Mahal




Symmetry exists in architecture all around
 the world.  The best known example of
          this is the Taj Mahal.
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).
2D Shapes and Symmetry


 After investigating the following
 shapes by cutting and folding,
            we found:
                  
an equilateral triangle has 3 internal
  angles and 3 lines of symmetry. 
 
  a square has 4 internal angles and 4
          lines of symmetry. 
                      
  a regular pentagon has 5 internal
  angles and 5 lines of symmetry.
                   
a regular hexagon has 6 internal angles
       and 6 lines of symmetry .
 
  a regular octagon has 8 internal angles
         and 8 lines of symmetry.
How many lines of symmetry to
 these regular polygons have?




                         Do you
                         see a
                         pattern?
What about these math symbols?
         Do they have symmetry?
Which of these flags have a
line of symmetry?


United States of     Canada
America




      Maryland       England
Click the
triangle to
               Turning a
see rotation
               figure around a
               point or a
               vertex
What is Rotational Symmetry?

 An image has Rotational
Symmetry if there is a point
in the image that the image
  can be turned around a
 certain number of degrees
   and still look the same.
How do you determine if an
   image has rotational
        symmetry?

1. Trace the image.
2. Rotate the image until it
matches up exactly.
3. Continue until you reach
your starting point.
Rotational Symmetry is
described by identifying the
    order of the figure.
             This triangle has
              an order of 3
            because there are
            3 positions where
            the triangle looks
                the same.
What is
    the
order for
   this
 figure?
Rotational Symmetry
                                         2
                    The order of
                    rotational
                    symmetry that
                    an object has is
                    the number of
                                                     1
    Order           times that it fits       Order
          3         on to itself
                                             2
    1               during a full
                    rotation of 3600




2               1

     Order
     3
Rotational Symmetry
What is the order of rotational symmetry of the shape below?
Rotational Symmetry
What is the order of rotational symmetry of the shape below?
                                  5




               4                                      1




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

                                  6


                   5                              1




                    4                            2


                                   3
                                 Order
                                 6
Equilateral Triangle
An equilateral triangle has rotational symmetry of order ?
Equilateral Triangle
An equilateral triangle has rotational symmetry of order ?   3
                                       3




                  2                                     1
Regular Pentagon
A regular pentagon has rotational symmetry of order ?




                   Pentagon
Regular Pentagon
A regular pentagon has rotational symmetry of order ?
Regular Pentagon
A regular pentagon has rotational symmetry of order ?       5
                                  5




               4                                        1




                      3                         2
Regular Hexagon
A regular hexagon has rotational symmetry of order ?




   Hexagon
Regular Hexagon
A regular hexagon has rotational symmetry of order ?
Regular Hexagon
A regular hexagon has rotational symmetry of order ?       6


                        5                        6




                4                                      1




                        3                    2
Rectangle
A rectangle has rotational symmetry of order ?




        Rectangle
Rectangle
A rectangle has rotational symmetry of order ?   2

                                                     2




            1
Parallelogram
A parallelogram has rotational symmetry of order ?




         Parallelogram
Parallelogram
A parallelogram has rotational symmetry of order ?   2


                                                         2




            1
Isosceles Triangle
An isosceles triangle has rotational symmetry of order ?
Isosceles Triangle
An isosceles triangle has rotational symmetry of order ?   1

                                     1
Scalene Triangle
An scalene triangle has rotational symmetry of order ?




         Scalene
Scalene Triangle
An scalene triangle has rotational symmetry of order ?   1


                                               1
Isosceles Trapezium
An isosceles trapezium has rotational symmetry of order ?




  Isos Trapezium
Isosceles Trapezium
An isosceles trapezium has rotational symmetry of order ?   1


                                                1
Trapezium
A trapezium has rotational symmetry of order ?




      Trapezium
Trapezium
A trapezium has rotational symmetry of order ?   1



                                            1
Kite
A kite has rotational symmetry of order ?




          Kite
Kite
A kite has rotational symmetry of order ?       1
                                            1




         Kite
Rotational Symmetry
    State the order of rotational symmetry for each shape below:
1                2                 3                     4



      Order 6            Order 2            Order 3                Order 2
5                    6                 7                 8



       Order 1           Order 3            Order 2                Order 5
9                 10                   11                 12


       Order 4           Order 1             Order 6                Order 8
Angle of rotation/order of
             rotation
 Square        90 degree       4
 Rectangle     180 degree      2
 Equilateral   120 degree      3
 Circle         nil/no limit   nil
Reflection
    (flip)
The result of a figure
 flipped over a line.
Click on this
trapezoid to
see
reflection.




     The result of a figure flipped over a line.
Which shapes show reflection,
  translation, or rotation?
Translation
  (Slide)
The action of sliding a
figure in any direction.
Click the Octagon
      to see
   Translation.
                    The act of sliding a figure in
                    any direction.
HOPE YOU ALL
 ENJOYED.
  THANKS

Final symmetry presentation

Editor's Notes

  • #9 This type of symmetry is also called reflectional symmetry as the two parts reflect/match along each side of a dividing line ( or axis ).
  • #15 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 20 000 workers, 20 years (Encarta 97) and it is rumoured that they used 40 000 elephants to transport the materials.
  • #22 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?