Cambridge International Mathematics

C

A98° B

21 cm

15 cm

P

R

Q

4.8 km

38°

6.7 km

K

L M

10.3 m

72°

14.8 m

AB

C

9m 11 m

14 m

Example 9 Self Tutor

Find the size of ABC in the given figure.b

Give your answer correct to 1 decimal place.

cosB=

a^2 +c^2 ¡b^2

2 ac

) cosB=

112 +8^2 ¡ 92

2 £ 11 £ 8

) B= cos¡^1

μ

112 +8^2 ¡ 92

2 £ 11 £ 8

¶

) B¼ 53 : 8 o

So, AbBC measures about 53 : 8 o.

EXERCISE 29D

1 Find the value ofxin:

abc

de f

2 Find the length of the remaining side in the given triangle:

abc

3 Find the measure of all angles of:

A

B C

B

8m 9m

11 m

5m

80°

xm

6m

10 cm

xcm

140°

11 cm

3.8 km

100°

5.3 km

xkm

3m

4m

x° 2m

9cm

12 cm

x°

7cm

8km

11 km

x°

14 km

590 Further trigonometry (Chapter 29)

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Y:\HAESE\IGCSE01\IG01_29\590IGCSE01_29.CDR Friday, 31 October 2008 9:51:46 AM TROY