Introduction to Geometry

1
Introduction to Geometry

• Form 1 Mathematics
• Chapter 6

2
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)

3
Points, Lines and Planes

• Points ?
• Lines ?
• Planes ?

4
Angles

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

5
Types of Angles (p.229)

• There are six types

6
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

7
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

8
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.

9
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 8 lines (Octa-)
• Number prefix (from wikipedia)

10
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 (????)

11
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

12
Types of Triangle (p.237)

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

13
Angle Sum of a Triangle

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

14
Solids (p.247)

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

Plane
Vertex
Curved surface
Edge
15
Drawing Solids

• Dotted lines
• Isometric Drawing

16
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

17
Polyhedra (???)

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

18
Model of Polyhedra

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

19
Dictation

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

20
Dictation

• Give the English name of the followings
• 1. ??
• 2. ??
• 3. ???
• 4. ???
• 5. ??
• 6. ?????

21
Dictation

• Give the English name of the followings
• 7. ??
• 8. ??
• 9. ???
• 10. ????
• 11. ?????
• 12. ?????
• Can you get them all?

22
Dictation Answers

• Here are the answers
• 1. ?? Line Segment
• 2. ?? Vertex
• 3. ??? Parallel Lines
• 4. ??? Perpendicular Lines
• 5. ?? Obtuse Angle
• 6. ????? Isosceles Triangle

23
Dictation Answers

• Next we have
• 7. ?? Circumference
• 8. ?? Diameter
• 9. ??? Diagonal
• 10. ???? Regular Polygon
• 11. ????? Equilateral Pentagon
• 12. ????? Equiangular Hexagon
• Can you get them all?

24
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)

25

• Enjoy the world of Mathematics!