Page 123 - Mathematics Coursebook

12.3 Constructing triangles

12.3 Constructing triangles 5 cm

You need to be able to do two types of triangle construction. 42°
In the #rst, you are given two sides and the angle between them. 7.5 cm
!is angle is the included angle. !is is known as SAS, which
stands for Side Angle Side.
In the second, you are given two angles and the side between them.
!is side is the included side. !is is known as ASA, which stands for
Angle Side Angle.
You need a ruler and a protractor to draw these triangles accurately. 52° 60º
3
4
1
2
8
7
5
6
cm
16 cm
Worked example 12.3
80
90
Make an accurate drawing of the following triangles.
70
100 110
100
80
a 60 120 b 110 70 60
120
4 cm 50 130 50
130
40º 40 140 30º 60º 40
140
30 150 6 cm 8 cm 30 150
a 20 160 20 160 First, draw the side 6 cm long.
10 170 cm 1 2 3 4 5 6 7 8 10 170
0 180 0 180
70 80 90 100 110 120
60 110 100 80 70
50 120 60 130
40 140 130 50 40 8 Use a protractor to measure the angle of 40° from
140
30 150 30 150 the left-hand end of the base line. Mark it with a
20 160 7 20 160 small point.
10 170 6 10 170
180 0 180
0
5
4
8
3 7
2 6
5
1
cm 4 Now draw the second side, 4 cm long.
3
2
1
cm

4 cm Finally draw the third side of the triangle. Label the
4 cm sides and angles with their correct measurements.

40º
40º 6 cm
6 cm

122 12 Constructions