Symmetry

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Symmetry
MTH 2-19a MTH 3-19a
Line Symmetry
Rotational (Order) Symmetry
Creating Rotational Symmetry
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Translational Symmetry
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Starter Questions
MTH 2-19a MTH 3-19a
Q1. Calculate
Q2. If 1 bar of chocolate costs 65p. How much
will 1000 bars cost. Give your answer in s.
Q3. Round to 1 decimal place
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Q4. Convert to 24 hrs clock
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Line Symmetry
MTH 2-19a MTH 3-19a
Learning Intention
Success Criteria

1. Understand the term line symmetry.

1. To revise line symmetry.

1. Complete Drawings given the line of symmetry.

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Line Symmetry
MTH 2-19a MTH 3-19a
A line symmetry occurs in a shape if, when the
shape is folded over the line the two pieces
either side of the line, are exactly the same.
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Line SymmetryThe Square
MTH 2-19a MTH 3-19a
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Line SymmetryThe rectangle
MTH 2-19a MTH 3-19a
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Line SymmetryThe square
MTH 2-19a MTH 3-19a
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Line SymmetryThe Rhombus
MTH 2-19a MTH 3-19a
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Line SymmetryThe Parallelogram
MTH 2-19a MTH 3-19a
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No lines of symmetry !
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Line SymmetryThe Equilateral Triangle
MTH 2-19a MTH 3-19a
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Line SymmetryThe Trapezium 1
MTH 2-19a MTH 3-19a
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Line SymmetryThe Trapezium 2
MTH 2-19a MTH 3-19a
No lines of symmetry !
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Line SymmetryThe Hexagonal
MTH 2-19a MTH 3-19a
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Line Symmetry
MTH 2-19a MTH 3-19a
Example Complete the rest of the shape given
the line of symmetry.
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Creating Half-TurnSymmetry
MTH 2-19a MTH 3-19a
Your turn ! Exercise 1 Page 81
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Starter Questions
MTH 2-19a MTH 3-19a
Q1. Round the following to the first decimal
place.
(a) 153.37 (b) 261.55
Q2. What fraction is the green area. What
fraction is the grey area.
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Q3. A pencil costs 22p. How much does a 1000
cost. Put your answer in s.
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Rotational Symmetry
MTH 2-19a MTH 3-19a
Learning Intention
Success Criteria

1. Understand the terms rotational symmetry.

1. To explain rotational symmetry for a shape.

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Rotational Symmetry
MTH 2-19a MTH 3-19a
1. Draw this shape into your jotter.
2. Use the tracing paper to make a copy of this
shape.
3. Turn the tracing paper through 180 degrees
about the dot.
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This new shape has HALF - TURN symmetry
This dot is called the centre of symmetry
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Rotation Symmetry Half Turn
MTH 2-19a MTH 3-19a
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All these shapes have order 2
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Rotation Symmetry Order
MTH 2-19a MTH 3-19a
The order of symmetry is the number of times a
shape looks the same in one complete turn.
Has order 2
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Has order 3
Has order 4
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Rotational Symmetry
MTH 2-19a MTH 3-19a
Your turn ! Exercise 2 Page 82
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Starter Questions
MTH 2-19a MTH 3-19a
Q1. Calculate
Q2. What is the time difference between 8.15am
and 100pm
P20cm
Q3.
A25cm2
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5cm
Q4. Find the perimeter and area of the square.
Q5. Find the order of rotational symmetry for
the shape opposite.
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5
1
4
3
2
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Creating Half-TurnSymmetry
MTH 2-19a MTH 3-19a
Learning Intention
Success Criteria

1. Understand the terms half-turn symmetry.

• To explain how we can
• create half-turn symmetry for a shape.

1. Draw the other half of a shape such that it has
   half-turn symmetry.

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Creating Half-TurnSymmetry
MTH 2-19a MTH 3-19a
Task 1 Draw the complete shape you get after it
has been rotated through 180 degrees about the
point.
Task 2 Do the same for this shape
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Creating Half-TurnSymmetry
MTH 2-19a MTH 3-19a
Task 3 Do the same for this shape
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If you find it difficult to work out the new
shape 1. Try tracing the shape first 2. Then
rotate tracing paper 180 deg about the point.
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Creating Half-TurnSymmetry
MTH 2-19a MTH 3-19a
Your turn ! Exercise 3 Page 85
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Starter Questions
MTH 2-19a MTH 3-19a
Q1. Calculate
Q2. What is the time difference between 8.15am
and 100pm
Q3.
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Q4. (-2) (-3)
Q5. How many lines of symmetry does regular
hexagon have.
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Translational (slide)Symmetry
MTH 2-19a MTH 3-19a
Learning Intention
Success Criteria

1. Understand the terms translational, slide
   congruent and tile.

• To explain the meaning of
• Translational (slide) symmetry using tile
  patterns.

1. Identify shapes that tile.

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• Construct a tile pattern
• for shapes.

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Translational (slide)Symmetry
MTH 2-19a MTH 3-19a
Exactly the same shape and size !
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A shape that tiles can be completely surrounded
by congruent shapes WITHOUT leaving any gaps.
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Translational (slide)Symmetry
MTH 2-19a MTH 3-19a
Is this a tile pattern ?
No because there are gaps
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Translational (slide)Symmetry
MTH 2-19a MTH 3-19a
Write down as many tile patterns as you can that
you see every day.
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Translational (slide)Symmetry
MTH 2-19a MTH 3-19a
Your turn ! Exercise 4 Page 87
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