1. Introduction to Geometry
Form 1 Mathematics
Chapter 6
Introduction to Geometry

2. Reminder Lesson requirement Before lessons start Textbook 1A
Workbook 1A
Notebook (and folder)
Before lessons start
Desks in good order!
No rubbish around!

3. Revision on Geometry Basic concepts of Geometry
Points 點
Lines 線
Planes 面
(Solids) 體
Other concepts of Geometry
Angles 角
Parallel Lines 平行線
Perpendicular Lines 垂直線

4. Naming
Points 點
Lines 線
Planes 面

5. Angles
Angles:
Name of angles (middle letter is vertex!)

6. Types of Angles (p.229)
There are six types:

7. Types of Angles (p.229)
Note: Any two line segments that meet each other form two angles.
We name x as “DAC”, and we name y as “the reflex angle DAC”.

8. Parallel lines (p.231)
When two lines in the same plane, but they do not intersect each other, they are called parallel lines (平行線)
A pair of parallel lines is denoted by a pair of arrows (箭號)
We write “AB // CD”

9. Perpendicular lines (p.232)
When two lines in the same plane are intersecting at right angle (90), they are called perpendicular lines (垂直線)
A right angle will be clearly shown in a pair of perpendicular lines
We write “AB  CD”

10. Time for Practice Pages 233 – 234 of Textbook 1A
Questions 1 – 9
Pages 107 – 110 of Workbook 1A
Questions 1 – 8

11. Plane Figure (p.235)
Any shape enclosed by lines in the same plane is called Plane Figure.

12. Circle (p.235)
All points on the circle (circumference 圓周) are at the same distance (radius半徑) from the a fixed point (centre 圓心).
Diameter (直徑) is 2 x Radius (d = 2r)
C = d x  (圓周率) or C = 2r
  … r C d

13. Triangle (p.237) Triangles are formed by three straight lines
Its name depends on its angles

14. Time for Practice Page 238 of Textbook 1A Page 111 of Workbook 1A
Class Practice
Page 111 of Workbook 1A
Questions 1 – 2

15. Angle Sum of a Triangle Sum of angles of a triangle is 180
a + b + c = 180 (Straight angle = 180)

16. Time for Practice Page 240 of Textbook 1A
Class Practice
Pages 114 – 115 of Workbook 1A
Questions 7 and 10

17. Polygons (p.242)
The name of the polygons depends on the number of straight lines:
Triangle 3 lines (Tri-)
Quadrilateral 4 lines (Quadri-)
Pentagon 5 lines (Penta-)
Hexagon 6 lines (Hexa-)
Octagon ? lines (Octa-)
Number prefix (from wikipedia)

18. Polygons (多邊形) (p.242)
Diagonal (對角線) is the line segment joining any two non-adjacent (不相鄰) vertices (頂點 vertex)
A line segment joining two adjacent vertices is called a side (邊)
Same side  Equilateral (等邊) polygon
Same angle  Equiangular (等角) polygon
Both  Regular polygon (正多邊形)

19. Time for Practice Page 244 of Textbook 1A
Class Practice
Pages 112 – 113 of Workbook 1A
Questions 3 and 5

20. Compasses and Rulers Parallel lines: p.231 Perpendicular lines: p.232
Circle: p.236
Triangles: p.241

21. Reminder CBQ – Chapter 5 SHW (I) – Chapter 6 SHW (II) – Chapter 6
Correction! (ALL questions)
Must have signature!!!!
Today
SHW (I) – Chapter 6
SHW (II) – Chapter 6
25 Jan (Fri)

22. Enjoy the world of Mathematics!
Ronald HUI