Introduction to Geometry

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# Introduction to Geometry - PowerPoint PPT Presentation

Form 1 Mathematics Chapter 6. Introduction to Geometry. Reminder. Drawing Exercises &amp; Dictation Today!!!! SHW (III) &amp; 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.

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Form 1 Mathematics

Chapter 6

### Introduction to Geometry

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 “ABCD”
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-)
• 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)

C

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 = 2r
•   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)
Solids (p.247)
• Solids are 3-D (three-dimensional) figures.

Plane

Vertex

Curved surface

Edge

1 cm

1 cm

1 cm

Drawing Solids
• Dotted lines
• Isometric Drawing
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
Polyhedra (多面體)
• When all faces of a solid are polygons only, it is called a polyhedron.

Yes! No!

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
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?
• 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
• 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)