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# Introduction to Geometry - PowerPoint PPT Presentation

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.

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

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Chapter 6

### Introduction to Geometry

• 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 點

• Lines 線

• Planes 面

• Angles:

• Name of angles (middle letter is vertex!)

• There are six types:

• 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”

• 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”

• 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)

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…

• Triangles are formed by three straight lines

• Its name depends on its angles

• Sum of angles of a triangle is 180

• a + b + c = 180 (Straight angle = 180)

• Solids are 3-D (three-dimensional) figures.

Plane

Vertex

Curved surface

Edge

1 cm

1 cm

Drawing Solids

• Dotted lines

• Isometric Drawing

• 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.

• Words on the PowerPoint files

• 12 questions

• Write down the answers one-by-one

• Final minutes for revision

• 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

• 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?

• 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)

Ronald HUI