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## PowerPoint Slideshow about ' Introduction to Geometry' - ernie

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Reminder

- Drawing Exercises & Dictation
- 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)

Points, Lines and Planes

- Points 點
- Lines 線
- Planes 面

Angles

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

Types of Angles (p.229)

- There are six types:

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”

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 willbe clearly shownin a pair of perpendicular lines
- We write “ABCD”

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.

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)

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)

r

d

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 = 2r
- 3.14159 26535 897…

Types of Triangle (p.237)

- Triangles are formed by three straight lines
- Its name depends on its angles

Angle Sum of a Triangle

- Sum of angles of a triangle is 180
- a + b + c = 180 (Straight angle = 180)

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

Model of Polyhedra

- The connected planes of a polyhedron are called a net.

Dictation

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

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

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?

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

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?

Reminder

- Drawing Exercises & Dictation
- 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)

Enjoy the world of Mathematics!

Ronald HUI

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