The first three letters of your name • Can you fold the letters in a way that the top half exactly covers the bottom half? • If you can draw a line !
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The first three letters of your name
• Can you fold the letters in a way that the top half exactly covers the bottom half?
• If you can draw a line !
Symmetry in Letters !
Symmetry
What is Symmetry?
• If a shape can be folded in half so that one half fits exactly on top of the other, than we say that the shape has got line symmetry.
• The fold is called a line of symmetry, it divides the shape into two equal parts!
• The lines of symmetry may be vertical, horizontal or diagonal
1 LoSOne Line of Symmetry
Vertical lines of symmetry
Horizontal lines of symmetry
Diagonal lines of symmetry
RectangleThe Rectangle Problem
A rectangle has only 2 lines of symmetry and not 4 like the square
To see this consider the following:
Half a rectangleMirror Line
The Rectangle Problem
A rectangle has only 2 lines of symmetry and not 4 like the square
To see this consider the following:
Half a rectangleMirror Line
A reflection in the diagonal would produce a kite!
Regular
Regular Polygons
Equilateral Triangle Square Regular Pentagon
Regular Hexagon Regular Octagon
Regular polygons have lines of symmetry equal to the number of sides/angles that they possess.
Identify the Lines of Symmetry
Identify the Lines of Symmetry
Identify the Lines of Symmetry
Symmetry in Real Life
• God made many things in nature symmetrical!
• Humans like to follow God’s footsteps when making objects because in this way things look nicer !
How many ?
• An object may have
One line of Symmetry
Many lines of Symmetry
No lines of Symmetry
A circle ?
INFINITE LINES OF SYMMETRY !
Mix 1
How many lines of symmetry for each shape?
4 3
5 8
5
Formula one Book
Pg 49 No. 1 and No.2
Get square mirror again
HAPPY WEEKEND!
Mix 32 5 3
2 4
How many lines of symmetry for each shape?
Mix 4
How many lines of symmetry for each shape?
6 2 4
1 2 1
Mix 5
How many lines of symmetry for each shape?
1 2 4
5 3
Tracing 1
Reflections
object
Mirror Line
Reflect the object shape in the mirror line shown.
object
Mirror Line
Reflect the shape in the mirror line shown.
Reflections
Mark position of vertices, draw image of shape.
Mirror Line
Reflections
object image
Tracing 2
Reflections
Mirror Line
Reflect the object shape in the mirror line shown.object
Reflections
Mirror Line
Reflect the object shape in the mirror line shown.object
Mark position of vertices and draw image of shape.
Reflections
Mirror Line
Reflect the object shape in the mirror line shown.object
Mark position of vertices and draw image of shape.
image
What letter would you get if you reflected each shape in its corresponding mirror line?
STARTER
What letter would you get if you reflected each shape in its corresponding mirror line?
STARTER
What letter would
you get if you
reflected each
shape in its
corresponding
mirror line?
What letter would you get if you reflected each shape in its corresponding mirror line?
Shape 1• Look at this shape.
• Can you spot the vertical reflection of the shape on the next slide? Hold up the correct letter when asked.
A B
C D
Congratulations!The correct answer is B!
Shape 2• Look at this shape.
• Can you spot the vertical reflection of the shape on the next slide? Hold up the correct letter when asked.
A B
C D
Congratulations!The correct answer is A!
Shape 3• Look at this shape.
• Can you spot the horizontal reflection of the shape on the next slide? Hold up the correct letter when asked.
A B
C D
Congratulations!The correct answer is D!
Shape 4• Look at this shape.
• Can you spot the horizontal reflection of the shape on the next slide? Hold up the correct letter when asked.
A B
C D
Congratulations!The correct answer is B!
Shape 5• Look at this shape.
• Can you spot the diagonal reflection of the shape on the next slide? Hold up the correct letter when asked.
A B
C D
Congratulations!The correct answer is A!
Shape 6• Look at this shape.
• Can you spot the diagonal reflection of the shape on the next slide? Hold up the correct letter when asked.
A B
C D
Congratulations!The correct answer is D!
Reflections
Vertical lines become Horizontal
Diagonal lines remain Diagonal
Reflections
Horizontal lines become Vertical
Vertical lines become Horizontal
Diagonal lines remain Diagonal
2.
3.
4.
5.
Another kind of symmetry?
What do you think we call this kind of symmetry?
TOP Centre of rotation
Rotational Symmetry !
We say a shape has ROTATIONAL SYMMETRY if it fits exactly into itself (looks exactly THE SAME)
when it is rotated.
How many times does this shape fit into itself?
TOP
We say it has rotational symmetry of order 4
A shape may have NO Rotational Symmetry
A shape is said to haveNO Rotational Symmetry (Rotational Symmetry of ORDER 1)
If it fits onto itself only ONE TIME
Equilateral Triangle
An equilateral triangle has rotational symmetry of order ?
12
3
3
Square
A square has rotational symmetry of order ?
Square
Square
A square has rotational symmetry of order ?
Square
A square has rotational symmetry of order ?
12
3
4
4
Regular Pentagon
A regular pentagon has rotational symmetry of order ?
Regular Pentagon
A regular pentagon has rotational symmetry of order ? 5
1
23
4
5
Hexagon
Regular Hexagon
A regular hexagon has rotational symmetry of order ?
Regular Hexagon
A regular hexagon has rotational symmetry of order ?
1
23
4
5 6
Regular Hexagon
A regular hexagon has rotational symmetry of order ? 6
Regular PolygonsWhat did we say a Regular Polygon is?
A regular polygon is a shape which has:• All sides equal
• All angles equal
Examples ?
What did we say about lines of symmetry of regular polygons?
Regular polygons have lines of symmetry equal to the number of sides/angles that they possess.
What then can we conclude?
Regular polygons have order of rotational symmetry equal to the number of sides/angles that they have.
Rectangle
Rectangle
A rectangle has rotational symmetry of order ?
2
1
2
Rectangle
A rectangle has rotational symmetry of order ?
Home Work from FORM 1 Maths Pack
Pg 17 ALL Page (short questions)
Pg 18 No.5 and No.7
TEST & REVISION SESSIONS
Date: Friday 4th April
Topics: Data Handling & Symmetry
Sub-topics : • Tally Charts• Bar Charts• Pie Charts• Finding the lines of symmetry of a shape• Drawing the other half of shapes in lines of symmetry• Finding the Order of Rotation of a shape
Questions 2
Rotational Symmetry
State the order of rotational symmetry for each shape below:
13 14 15 16
17 18 19 20
21 22 23 24
Order 4 Order 1 Order 2 Order 5
Order 2 Order 4 Order 6 Order 3
Order 5 Order 4 Order 3 Order 1
Worksheet 2
Rotational SymmetryState the order of rotational symmetry for each shape below:
13 14 15 16
17 18 19 20
21 22 23 24
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