Angle Properties

1
Angle Properties
Revision of Level E
Interior / Exterior Angles
Angles in Time
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2
Starter Questions
5 cm
3 cm
3 cm
10 cm
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3
Angle Properties
Revision of Level E
Learning Intention
Success Criteria

1. Remember basic properties for angles.

1. We are reviewing angle properties.

1. Apply properties to solve angle problems..

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4
Angle Properties
Revision of Level E
MTH 3-17a
65o
Two angles making a straight line add to 180o
145o
Angles round a point Add up to 360o
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90o
146o
146o
3 angles in a triangle ALWAYS add up to 180o.
angles opposite each other at a cross are equal.
5
Angle Properties
Revision of Level E
MTH 3-17a
ALL angles in an equilateral triangle are 60o
Two angles in a isosceles Are equal
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h
is corresponding to d and must be 115o
b
is opposite to d and must be 115o
c
is must be 65o (straight line)
e
is alternate to c and must also be 65o
6
Angle Properties
Revision of Level E
Now try Exercise 1 Ch3 (page 21) Copy out shapes
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7
Starter Questions
7 cm
3 cm
5 cm
20 cm
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8
Polygons
Interior and Exterior Angles
Learning Intention
Success Criteria

1. To know the term polygon.

1. We are exploring interior and exterior angles of
   a polygon .

1. Understand steps for calculating the interior and
   exterior angle of a polygon.

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9
Polygons
Interior and Exterior Angles
A polygon is a many-sided closed straight-lined
figure This 5-sided (polygon) is called a
PENTAGON
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Irregular Pentagon
10
Polygons
Interior and Exterior Angles
A polygon is a many-sided closed straight-lined
figure
If all the sides and angles are the same it is
called REGULAR POLYGON. We will only be dealing
with regular polygons in this section.
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Pentagon
Hexagon
Octagon
11
Polygons
Interior and Exterior Angles
Some useful points about regular polygons

• All the triangles around the centre are
  isosceles.

• Angle at the centre is 360o

• To find one angle at the centre, take 360o and
  divide it by how many triangles you have

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12
Level F - Polygons Worksheet Ex2
MTH 3-17a
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13
Polygons
Interior and Exterior Angles
MTH 3-17a
Now try Exercise 2 Ch3 (page 23) Q1-Q6 Use
worksheet Provide
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14
Polygons
Interior and Exterior Angles
What you should have found
Interior angle 180 (360n)
n Number of sides
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eg . A hexagonal has interior angle is
Interior angle 180 (3606) 120o
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Polygons
Interior and Exterior Angles
A
B
E
This is called the Exterior angle
O
Pentagon
Q
C
D
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Exterior angle 180 interior angle
eg . For the pentagon above
Exterior angle 180 108 72o
16
Polygons
Interior and Exterior Angles
MTH 3-17a
Now try Exercise 2 Ch3 (page 23) Q8-Q9 Use
worksheet Provide
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17
Starter Questions
10 cm
4 cm
3 cm
7 cm
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18
Polygons
Interior and Exterior Angles
MTH 3-17a
Practice on Angles Now try Exercise 3 Ch3 (page
26)
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