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Form 1 Mathematics
Chapter 9
Lesson requirement Textbook 1B Workbook 1B Notebook Folder
Before lessons start Desks in good order! No rubbish around! No toilets!
Reflectional Symmetry (反射對稱 , p.78)
Rotational Symmetry (旋轉對稱 , p.80)
4 lines of symmetry
Lines of symmetry
Centre
Of
Rotation
3-fold rotational symmetry
3-fold rotational symmetry
5-fold rotational symmetry
Centre
Of
Rotation
5-fold rotational symmetry
Centre
Of
Rotation
Pages 84 – 85 of Textbook 1B Questions 2 – 10
Pages 38 – 39 of Workbook 1B Questions 3 – 9
Four types of transformations:1. Translation2. Reflection3. Rotation4. Enlargement / reduction
Let’s look at this now
It translates the figure to the left by 1 unit.
A
B C
A’
B’ C’
A
B
CCArrow A is translated 4 units to the right and 2 units downwards to give Arrow C.
Four types of transformations:1. Translation2. Reflection3. Rotation4. Enlargement / reduction
Let’s look at this now
It reflects the figure
about the line of reflection
AB.
A
B
Figure A Figure B
Lin
e of
ref
lect
ion
What’s this line called?
Four types of transformations:1. Translation2. Reflection3. Rotation4. Enlargement / reduction
Let’s look at this now
Centre of rotation
It rotates the figure anti-clockwisearound point G
by 90o.
G
What is point G called?
A’
A
B
C
D
E
╳O
E’
D’ C’
B’
The arrow ABCDE is rotated clockwise by 90° about the point O to obtain image A’B’C’D’E’
A
B C ╳O
A’B’
C’
C’’ B’’
A’’
C’’’
B’’’A’’’
Four types of transformations:1. Translation2. Reflection3. Rotation4. Enlargement / reduction
Let’s look at this now
The robot enlarges the figure to 2 units long and 2 units high
The robot ??? the figure to ?? units ???? and ?? units ????
Another way: The robot ENLARGES the figure by 2 TIMES
The robot enlarges the figure by 2 times
This is called ENLARGEMENT.
A B
C
A’ B’
The robot reduces the figure to 1 unit long and 1 unit high
The robot ??? the figure to ?? units ???? and ?? units ????
Another way: The robot REDUCES the figure by ONE HALF (1/2)
The robot reduces the figure by one half
This is called REDUCTION.
A B
C
A’ B’
Pages 100 – 101 of Textbook 1B Questions 1 – 14
Pages 40 – 41 of Workbook 1B Questions 1 – 2
B A
C
A’
C’
A’
C’
What is the length of A’B’?
( 18 ÷ 3 ) x (3 + 3 + 3) = 54
The length of A’B’ is 54 units after the enlargement.
Three different effects of transformations on coordinates system:
1. Translation2. Reflection3. Rotation
Translation of a point (e.g. move to the right by 7 units)
A (–3 , 6) A’ (4 , 6)
Moveto the right by a units
A (x, y) A’ (x+a, y)
Translation of a point (e.g. move to the left by 5 units)
A (4 , 3) A’ (–1, 3)
Moveto the left by a units
A (x, y) A’ (x–a, y)
Translation of a point (e.g. move upwards by 7 units)
A (–3 , 6) A’ (–3 , 13)
Move upwards by a units: A (x, y) A’ (x, y+a)
Move downwards by a units: A (x, y) A’ (x, y–a)
Translation of a line segment (e.g. move to the left by 4)
Point first
Then line
Translation of a plan figure(e.g. move downwards by 6)
Point first
Then shape
Reflection of a point(e.g. Reflect along x-axis)A (4 , 2) A’ (4 , –2)
Reflectalong x-axis
A (x, y) A’ (x, –y )
Reflection of a point (e.g. Reflect along y-axis)A (4 , 2) A’ (–4 , 2)
Reflectalong y-axis
A (x, y) A’ (–x, y )
Reflection of a line segment (e.g. Reflect along y-axis)
Point first
Then line
Reflection of a plan figure (e.g. Reflect along y-axis)
Point first
Then shape
Rotation of a point(e.g. Rotate about OriginAnti-clockwise by 90)A (4 , 2) A’ (–2 , 4)
Reflect about Origin by 90 anti-clockwise
A (x, y) A’ (–y, x)
Rotation of a point(e.g. Rotate about OriginAnti-clockwise by 180)A (4 , 2) A’ (–4 , –2)
Reflect about Origin by 180 anti-clockwise
A (x, y) A’ (–x, –y)
Rotation of a point(e.g. Rotate about OriginAnti-clockwise by 270)A (4 , 2) A’ (2 , –4)
Reflect about Origin by 270 anti-clockwise
A (x, y) A’ (y, –x)
Pages 114 – 115 of Textbook 1B Questions 5 – 17
Pages 43 – 44 of Workbook 1B Questions 1 – 4
Result of Close Book Quiz Full mark: 40 and 10 bonus Highest: 38 Lowest: 4 Average: 18.1 Number of students between 10 – 19: 12 Number of students between 0 – 9: 8
Major Problems Cannot get the base and height of the figure Cannot calculate the areas No “units”, No “sq. units”, Wrong use of
units
Result of Close Book Quiz 9th place: CHAN Wa Pan, Ben 6th place: CHEN Yi, David
HUNG Nok Yin, AngusWU SHAN Hao Yi
4th place: CHAN Tsz Long, Sam FU Ling Yin, Larry
3rd place: LAU Cheuk Hei, Anson 2nd place: LI Ming Chun, Edward 1st place: LI Sai Kong
Congratulations!!!!!! Well done!!!!!!
Missing Homework, Re-do Homework Today!
SHW (III) 15 Mar (Fri)
Open Book Quiz 15 Mar (Fri)
Close Book Quiz 19 Mar (Tue) – To be confirmed
Enjoy the world of Mathematics!
Ronald HUI