Page 124 - Mathematics Coursebook

12.3 Constructing triangles

cm 1 2 3 4 5 6 7 8
cm 1 2 3 4 5 6 7 8
b Start by drawing the base line, 8 cm long.
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90 80 70
70 100 90 80 70 60 120 110 100 110 120 130
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50 60 120 110 100 110 120 130 Use a protractor to measure the angle of 30° from the
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40 140 130 50 40 140 left-hand end of the base line. Mark it with a small
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30 150 30 150 point. 20 160 20 160
20 160 20 160 10 170
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10 170 10 170 Draw a line through the 30° mark 10 0 180
180
0
0 180 0 180
70 80 90 80 70
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Use a protractor to measure the angle of 60° from 50 130 60 120 110 100 110 120 130
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90 80 70
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the right-hand end of the base line. Mark it with a 40 140 40 140
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130
100 110 120 130
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small point. 30 150 40 140 40 30 150 20 30 150 30 150 160
140
20 160 20 160 10 170 160 20 10 170
10 170 10 170 0 180 0 180
0 180 0 180
Draw a line through the 60° mark that crosses the 30° line.
30° 60° Label the sides and angles with their correct measurements.
8 cm
) Exercise 12.3 60° 30° 8 cm 60°
30°
8 cm
1 Draw an accurate copy of each of these triangles.
a b c
6 cm6 cm6 cm
5 cm5 cm5 cm 4 cm4 cm4 cm
50º50º50º 45º45º45º 30º30º30º
6.5 cm
7 cm 7 cm 7 cm 6.5 cm6.5 cm 4.5 cm4.5 cm4.5 cm
2 Draw an accurate copy of each of these triangles.
a b c
40º 40º 40º 50º 50º 50º 35º 35º 35º 55º 55º 55º 55º 55º 55º 40º 40º 40º
6 cm6 cm6 cm 8.5 cm8.5 cm8.5 cm 9.2 cm9.2 cm9.2 cm
3 a Draw an accurate copy of triangle ABC. A
b Measure and write down the length of AC. 6.5 cm
c Measure and write down the size of angle BCA. 48º C
4 a Draw an accurate copy of triangle PQR. B 8.7 cm
b Measure and write down the length of PQ. P
c Measure and write down the length of PR.
d Measure and write down the size of angle QPR.
e Work out the total of the three angles in the triangle. Q 38º 62º R
f Have you have drawn your triangle accurately? 7.6 cm
Give a reason for your answer.
5 Draw an accurate copy of each of these triangles.
a b
5.2 cm 3 cm
120° 150°
c 6 cm 5.5 cm
d
40° 125° 108° 27°
4.8 cm 9.3 cm
12 Constructions 123