Lines and Points of Symmetry If there is a common point of...
Transcript of Lines and Points of Symmetry If there is a common point of...
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Symmetry
Lines and Points of Symmetry
•Some figures can be folded so that the two halves match exactly.
The fold is a line of reflection called
____________________________.
•If there is a common point of reflection for all points on a figure,
the point of reflection is called a
_____________________________.
Examples:
Line of Symmetry
Point of Symmetry
1 2Infinitely
Many
No - Point
Symmetry
Yes - Point
Symmetry
Yes - Point
Symmetry
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Symmetry
We are familiar with identifying symmetry through reflection, today we
will look at symmetry through rotation.
First, what point do we rotate a shape about.
The intersection of the lines of symmetry by reflection is the point we
will rotate the shape about.
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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.None
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Rotational Symmetry
None
1
2
Order 2
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.
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Rotational Symmetry
None
1
2
Order 2
12
3
Order 3
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.
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Rotational Symmetry
None
1
2
Order 2
12
3
Order 312
3 4
Order 4
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.
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1
23
4
5
What is the order of rotational symmetry of the shape below?
Order 5
Rotational Symmetry
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1
23
4
5
At what angle (magnitude) does the shape have rotational
symmetry?
Order 5
Angle of Rotational Symmetry
Angle of
symmetry:
360o
÷ Order
360o
÷ 5
Magnitude
of
rotational
symmetry
is 72o
360o
÷ 5
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1
2
3
4
5
What is the order and magnitude of rotational symmetry of the
shape below?
Order 6
Rotational Symmetry
6Angle of
symmetry:
360o
÷ Order
Magnitude
of
rotational
symmetry
is 60o
360o
÷ 6
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Equilateral Triangle
An equilateral triangle has rotational symmetry of order
and magnitude?
12
3
3
Angle of
symmetry:
360o
÷ Order
Magnitude
of
rotational
symmetry
is 120o
360o
÷ 3
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Square
A square has rotational symmetry of what order and
magnitude?
Square
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Square
A square has rotational symmetry of what order and
magnitude?
12
3
4
4Angle of
symmetry:
360o
÷ Order
Magnitude
of
rotational
symmetry
is 90o
360o
÷ 4
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Regular Pentagon
A regular pentagon has order and magnitude of rational
symmetry?5
1
23
4
5
Angle of
symmetry:
360o
÷ Order
Magnitude
of
rotational
symmetry
is 72o
360o
÷ 5
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1
23
4
5 6
Regular Hexagon
A regular hexagon has rotational symmetry of order ? 6
Angle of
symmetry:
360o
÷ Order
Magnitude
of
rotational
symmetry
is 60o
360o
÷ 6
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1
2
34
5
6
Regular Octagon
A regular octagon has rotational symmetry of order ? 8
7 8
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2
1
2
Rectangle
A rectangle has rotational symmetry of order ?
Angle of
symmetry:
360o
÷ Order
Magnitude
of
rotational
symmetry
is 180o
360o
÷ 2
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2
1
2
Parallelogram
A parallelogram has rotational symmetry of order ?
Angle of
symmetry:
360o
÷ Order
Magnitude
of
rotational
symmetry
is 180o
360o
÷ 2
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1
1
A trapezoid has rotational symmetry of order ?
Trapezoid
None
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2
1
A rhombus has rotational symmetry of order ?
Rhombus
2Angle of
symmetry:
360o
÷ Order
Magnitude
of rotational
symmetry is
180o
360o
÷ 2
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Worksheet 1
Rotational SymmetryState the order and magnitude of rotational symmetry for each shape below:
1 2 3 4
5 6 7 8
9 10 11 12
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Questions 1
Rotational SymmetryState the order of rotational symmetry for each shape below:
1 2 3 4
5 6 7 8
9 10 11 12
Order 6 Order 2 Order 3 Order 2
None Order 3 Order 2 Order 5
Order 4 None Order 6 Order 8
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Worksheet 2
Rotational Symmetry HomeworkState the order and magnitude of rotational symmetry for each shape below:
13 14 15 16
17 18 19 20
21 22 23 24
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Questions 2
Rotational SymmetryState the order of rotational symmetry for each shape below:
13 14 15 16
17 18 19 20
21 22 23 24
Order 4 None Order 2 Order 5
Order 2 Order 4 Order 6 Order 3
Order 5 Order 4 Order 3 None