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Form 3 Mathematics
Chapter 10
Basic concepts of Geometry
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Points
Lines
Planes
Solids
點
線
面
體
Other concepts of Geometry
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Angles
Parallel Lines
Perpendicular Lines
角
平行線
垂直線
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Points 點
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Lines 線
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Planes 面
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Any shape enclosed by line segments in the
same plane is called Plane Figure.
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Otherwise, it should be a curved surface.
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The name of the polygons depends on the
number of straight lines:
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Triangle
Quadrilateral
Pentagon
Hexagon
Octagon
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Number prefix (from wikipedia)
3 lines
4 lines
5 lines
6 lines
? lines
(Tri-)
(Quadri-)
(Penta-)
(Hexa-)
(Octa-)
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Diagonal (對角線) is the line segment
joining any two non-adjacent (不相鄰)
vertices (頂點 vertex)
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A line segment joining two adjacent vertices
is called a side (邊)
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Same side  Equilateral (等邊) polygon
Same angle  Equiangular (等角) polygon
Both
 Regular polygon (正多邊形)
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Solids are 3-D (three-dimensional) figures.
Vertex
Plane
Edge
Curved
surface
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Dotted lines
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Isometric Drawing
1 cm
1 cm
1 cm
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When all faces of a solid are polygons only, it
is called a polyhedron.
Yes!
No!
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F +V – E = 2
Vertex
Face
Edge
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The connected planes of a polyhedron are
called a net.
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If we cut a solid at right angle to its length,
the plane is called a cross-section.
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If planes from the parallel cuts are the same,
the plane is a uniform cross-section
Enjoy the world of Mathematics!
Ronald HUI