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

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. 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

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’ 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 (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

BA C A’ C’ A’ C’ What is the length of A’B’? ( 18 ÷ 3 ) x ( ) = 54 The length of A’B’ is 54 units after the enlargement.

Three different effects of transformations on coordinates system: 1. Translation 2. Reflection 3. Rotation

Translation of a point (e.g. move to the right by 7 units) A (–3, 6)  A’ (4, 6) Move to 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) Move to 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) Reflect along x-axis A (x, y)  A’ (x, –y )

Reflection of a point (e.g. Reflect along y-axis) A (4, 2)  A’ (–4, 2) Reflect along 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 Origin Anti-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 Origin Anti-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 Origin Anti-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 9 th place:CHAN Wa Pan, Ben 6 th place:CHEN Yi, David HUNG Nok Yin, Angus WU SHAN Hao Yi 4 th place:CHAN Tsz Long, Sam FU Ling Yin, Larry 3 rd place:LAU Cheuk Hei, Anson 2 nd place:LI Ming Chun, Edward 1 st 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