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

2. Reminder Drawing Exercises & Dictation SHW (III) & OBQ
Today!!!!
SHW (III) & OBQ
30 Jan (Wed)
SHW (I), (II) Correction
1 Feb (Fri)
SHW (III), OBQ Correction
4 Feb (Mon)
CBQ
6 Feb (Wed)

3. Points, Lines and Planes

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

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

6. 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”

7. 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”

8. Plane Figure (p.235)
Any shape enclosed by line segments in the same plane is called Plane Figure.
Otherwise, it should be a curved surface.

9. Polygons (多邊形) (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 8 lines (Octa-)
Number prefix (from wikipedia)

10. 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)

11. 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

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

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

14. Solids (p.247) Solids are 3-D (three-dimensional) figures. Plane
Vertex
Plane
Curved surface
Edge

15. Drawing Solids
Dotted lines
Isometric Drawing
1 cm

16. Cross-section
If we cut a solid at right angle to its length, the plane is called a cross-section.
If planes from the parallel cuts are the same, the plane is a uniform cross-section

17. Polyhedra (多面體)
When all faces of a solid are polygons only, it is called a polyhedron.
Yes! No!

18. Model of Polyhedra
The connected planes of a polyhedron are called a net.

19. Dictation Words on the PowerPoint files 12 questions
Write down the answers one-by-one
Final minutes for revision
Are you ready?

20. Dictation Give the English name of the followings: 1. 線段 2. 頂點 3. 平行線
4. 垂直線
5. 鈍角
6. 等腰三角形

21. Dictation Give the English name of the followings: 7. 圓周 8. 直徑 9. 對角線
10. 正多邊形
11. 等邊五邊形
12. 等角六邊形
Can you get them all?

22. Dictation Answers Here are the answers: 1. 線段 Line Segment
2. 頂點 Vertex
3. 平行線 Parallel Lines
4. 垂直線 Perpendicular Lines
5. 鈍角 Obtuse Angle
6. 等腰三角形 Isosceles Triangle

23. Dictation Answers Next we have: 7. 圓周 Circumference 8. 直徑 Diameter
9. 對角線 Diagonal
10. 正多邊形 Regular Polygon
11. 等邊五邊形 Equilateral Pentagon
12. 等角六邊形 Equiangular Hexagon
Can you get them all?

24. Reminder Drawing Exercises & Dictation SHW (III) & OBQ
Today!!!!
SHW (III) & OBQ
30 Jan (Wed)
SHW (I), (II), Dictation Correction
1 Feb (Fri)
SHW (III), OBQ Correction
4 Feb (Mon)
CBQ
6 Feb (Wed)

25. Enjoy the world of Mathematics!
Ronald HUI