Cambridge International Mathematics

Challenge #endboxedheading

110 Lines, angles and polygons (Chapter 4)

6 Copy and complete:

Polygon Number of sides Sum of interior angles

pentagon

hexagon

octagon

7 Calculate the size of each interior angle for a regular polygon with:

a 12 sides b 18 sides

8 Solve forx:

ab

80°

x°

150°

95°

115°

x° x°

x°

x° x°

x° x°

x° x°

1aMeasure the angles at A, B, C, D and E and find

their sum.

b Repeat with two other ‘ 5 -point star’ diagrams of

your choosing.

c What do you suspect about the angle sum for all

‘ 5 -point star’ diagrams?

d Use deductive geometry to confirm your suspicion.

e Repeatatodbut with a ‘ 7 -point star’ diagram.

A

B

C

D

E

F

G

H I

J

P

Q

R

S

U T

V

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Y:\HAESE\IGCSE01\IG01_04\110IGCSE01_04.CDR Friday, 24 October 2008 12:21:32 PM PETER