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 ) Rotational Symmetry ( 旋轉對稱 )

1 axis of symmetry

4 axes of symmetry

6 axes of symmetry

2-fold rotational symmetry Centre Of Rotation

Centre Of Rotation 3-fold rotational symmetry

5-fold rotational symmetry Centre Of Rotation

4-fold rotational symmetry Centre Of Rotation

5-fold rotational symmetry Centre Of Rotation

3-fold 5-fold4-fold

Pages 84 – 85 of Textbook 1B Questions 2 – 10 Pages 38 – 39 of Workbook 1B Questions 3 – 9

Four types of transformations: 1. Translation 2. Reflection 3. Rotation 4. 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 C C Arrow A is translated 4 units to the right and 2 units downwards to give Arrow C.

Four types of transformations: 1. Translation 2. Reflection 3. Rotation 4. Enlargement / reduction Let’s look at this now

It reflects the figure about the line of reflection AB. A B

A B C D E A’ B’ F’ D’ E’ X Y F G C’ G’

Figure A Figure B Line of reflection What’s this line called?

Four types of transformations: 1. Translation 2. Reflection 3. Rotation 4. Enlargement / reduction Let’s look at this now

Centre of rotation

It rotates the figure anti-clockwise around point G by 90 o. G What is point G called?

A B C D E A’ B’ F’ D’ E’ X Y F G C’ G’

A’ A B C D E ╳O╳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╳O A’ B’ C’ C’’ B’’ A’’ C’’’ B’’’ A’’’

Four types of transformations: 1. Translation 2. Reflection 3. Rotation 4. 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

The robot reduces the figure by one half This is called REDUCTION.

A B C A’B’

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Pages 100 – 101 of Textbook 1B Questions 1 – 14 Pages 40 – 41 of Workbook 1B Questions 1 – 2

Missing Homework, Re-do Homework Today! SHW (I) and SHW (II) 11 Mar (Mon) External Review 13 Mar (Wed) Open Book Quiz 13 Mar (Wed) Close Book Quiz 15 Mar (Fri) – To be confirmed

Enjoy the world of Mathematics! Ronald HUI