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Angle Properties
Revision of Level E
Interior / Exterior Angles
Angles in Time
23-May-17
Created by Mr. Lafferty
Angle Properties
www.mathsrevision.com
Revision of Level E
o
120 95
115
o
Angles round a point
o
Add up to 360
34
o
34
146o
50
90o
o
angles opposite each other
at a cross are equal.
23-May-17
65o
Two angles making a
o
straight line add to 180
145o
146o
o
o
40
o
3 angles in a triangle ALWAYS
o
add up to 180 .
Created by Mr. Lafferty
Angle Properties
www.mathsrevision.com
Revision of Level E
Two angles in a isosceles
Are equal
h
b
c
e
ALL angles in an equilateral
o
triangle are 60
is corresponding to d and must be 115
is opposite to d and must be 115
o
o
is alternate to c and must also be 65
23-May-17
Created by Mr. Lafferty
c
o
h
o
is must be 65 (straight line)
d = 115
o
g
o
o
o
a
o
o
b
o
e
f
o
Polygons
Interior and Exterior Angles
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A polygon is a “many-sided closed straight-lined figure”
This 5-sided (polygon) is called a PENTAGON
Irregular Pentagon
23-May-17
Created by Mr. Lafferty
Polygons
Interior and Exterior Angles
www.mathsrevision.com
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.
Pentagon
23-May-17
Hexagon
Created by Mr. Lafferty
Octagon
Polygons
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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
72o
Pentagon
Interior Angle
23-May-17
60o
Hexagon
Created by Mr. Lafferty
45o
Octagon
Interior Angles
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Level F - Polygons Worksheet Ex2
Pentagon (5 sided)
Hexagon (6 sided)
Heptagon (7 sided)
Octagon (8 sided)
Nonagon (9 sided)
Decagon (10 sided)
23-May-17
Created by Mr. Lafferty
Polygons
Interior and Exterior Angles
www.mathsrevision.com
What you should have found :
Polygon sides
Sum of Angles
4
5
6
7
8
9
11
12
360 540 720 900 1080 1260 1440 1620 1800
Size of Interior Angle 90 108 120 129 135
Interior angle = 180 – (360÷n)
140
Interior angle = 180 – (360÷6) = 120o
Created by Mr. Lafferty
144
149
150
n = Number of sides
eg . A hexagonal has interior angle is:
23-May-17
10
Polygons
Interior and Exterior Angles
www.mathsrevision.com
A
E
B This is called the
“Exterior angle”
O
Pentagon
D
C
Q
Exterior angle = 180 – interior angle
eg . For the pentagon above :
Exterior angle = 180 – 108 = 72o
23-May-17
Created by Mr. Lafferty