3. 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.
4. 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.
7. At the beach there are
a variety of shells with line
symmetry.
8. Under the sea there are also
many symmetrical objects
such as these crabs
and this starfish.
9. Animals that have Line
Symmetry
Here are a few more great examples of
mirror image in the animal kingdom.
10. 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
11. Lines of Symmetry all around us
Which of these road signs have got lines of
symmetry?
12. 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.
13. REFLECTION IN WATER
If an object is
reflected in water it
is considered to
have line symmetry
along the waterline.
14. The Taj Mahal
Symmetry exists in architecture all around
the world. The best known example of
this is the Taj Mahal.
15. 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).
16. 2D Shapes and Symmetry
After investigating the following
shapes by cutting and folding,
we found:
27. 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.
28. 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.
29. 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.
31. 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
58. 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
59. Angle of rotation/order of
rotation
Square 90 degree 4
Rectangle 180 degree 2
Equilateral 120 degree 3
Circle nil/no limit nil
60. Reflection
(flip)
The result of a figure
flipped over a line.
This type of symmetry is also called reflectional symmetry as the two parts reflect/match along each side of a dividing line ( or axis ).
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.
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?
