Introduction to Geometry

1
Introduction to Geometry

• Form 1 Mathematics
• Chapter 6

2
Reminder

• Lesson requirement
• Textbook 1A
• Workbook 1A
• Notebook
• Folder
• Before lessons start
• Desks in good order!
• No rubbish around!
• SHW (II)
• Today!!!!!

3
Revision on Geometry

• Basic concepts of Geometry
• Points ?
• Lines ?
• Planes ?
• (Solids) ?
• Other concepts of Geometry
• Angles ?
• Parallel Lines ???
• Perpendicular Lines ???

4
Reminder on Naming

• Points ?
• Lines ?
• Planes ?

5
Angles

• Angles
• Name of angles (middle letter is vertex!)

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Types of Angles (p.229)

• There are six types

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Parallel lines (p.231)

• When two lines in the same plane, but they do not
  intersect each other, they are called parallel
  lines (???)
• A pair of parallel lines is denoted by a pair
  of arrows (??)
• We write AB // CD

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Perpendicular lines (p.232)

• When two lines in the same plane are intersecting
  at right angle (90?), they are called
  perpendicular lines (???)
• A right angle willbe clearly shownin a pair of
  perpendicular lines
• We write AB ? CD

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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.

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Polygons (???) (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 ? lines (Octa-)
• Number prefix (from wikipedia)

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Polygons (???) (p.242)

• Diagonal (???) is the line segment joining any
  two non-adjacent (???) vertices (?? vertex)
• A line segment joining two adjacent vertices is
  called a side (?)
• Same side ? Equilateral (??) polygon
• Same angle ? Equiangular (??) polygon
• Both ? Regular polygon (????)

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Compasses and Rulers

• Parallel lines p.231
• Perpendicular lines p.232
• Circle p.236
• Triangles p.241

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Circle (p.235)

• All points on the circle (circumference ??) are
  at the same distance (radius??) from the a fixed
  point (centre ??).
• Diameter (??) is 2 x Radius (d 2r)
• C d x ? (???)or C 2?r
• ? ? 3.14159 26535 897

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Triangle (p.237)

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

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Angle Sum of a Triangle

• Sum of angles of a triangle is 180?
• a b c 180? (Straight angle 180?)

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Time for Practice

• Page 246 of Textbook 1A
• Questions 15 17
• Pages 112 113 of Workbook 1A
• Questions 3 and 5

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Solids (p.247)

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

Plane
Vertex
Curved surface
Edge
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Drawing Solids

• Dotted lines
• Isometric Drawing

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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

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Polyhedra (???)

• When all faces of a solid are polygons only, it
  is called a polyhedron.
• Yes! No!

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Model of Polyhedra

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

22
Time for Practice

• Drawing Exercise
• Class Activities I IV
• Pages 256 257 of Textbook 1A
• Questions 4 11
• Pages 118 120 of Workbook 1A
• Questions 4 6

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Reminder

• Drawing Exercise
• 28 Jan (Mon)
• Dictation words on the PowerPoint files
• 29 Jan (Tue)
• SHW (III) Chapter 6
• 30 Jan (Wed)
• OBQ Chapter 6
• 30 Jan (Wed)
• CBQ Chapter 6
• 1 Feb (Fri) or 6 Feb (Wed)

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• Enjoy the world of Mathematics!