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Quick Check
1. Following are the steps of constructing an angle ABC of 70° using a protractor which is not in correct
order. Arrange them in the the correct order.
• Starting with 0° near point C, mark point A at 70° on the paper
• Place the protractor on the line segment BC such that the mid-point of the protractor is at point B and
zero edge along BC.
• Join BA.
• Draw a BC.
2. Draw an angle of 105° using ruler and compass.

activity
Construction of angles using set squares.
Material Required: Set squares (90°, 45°, 45° and 90°, 60°, 30°), paper, and pencil.

B

1. To draw angles of 30°, 45°, 60° and 90°. Draw ray 2 1 1 2
OA. Take the set square having angle 30° and place 3 3 4
the vertex of 30° at O and side along OA. Draw 5 4
ray OB along the other edge of set square to get 6 A
∠BOA = 30° 7
Similarly, we can get angles of 45°, 60°, and 90°. 10 30° 8
9

O

1 1
2
3
4
5
6
2
A 3
2. To draw an angle of 75°: Use the 45° set square as 5 4
well as the 30° set square to construct an angle of 6
75°. 7 7 1 2
As 75° = 45° + 30°, we have ∠ABC = 75° 8 5 6 3
4 4 5
9
3 6
10
2 7
1 8
B C

A

3. To draw an angle of 105°: Use both set square to
construct an angle of 105°.
As 105° = 45° + 60°, we have ∠ABC = 105°

B C

343 Construction of Basic Geometrical Shapes