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Practice Time 15A

1. Draw a line segment of length 4.7 cm using a ruler.

2. Construct AB of length 7.6 cm. From this, cut off AC of length 3.9 cm. Measure BC.
3. Draw line segment AB of length 4.1 cm. Construct CD such that the length of CD is twice that of AB.
4. Draw a line segment CD of 5.4 cm. Mark any point P on it. Through P, draw a (Use ruler and compasses)
perpendicular bisector.

5. Draw a line PQ. Take a point A outside it. Draw a line passing through A and perpendicular to PQ.
6. Draw a line segment PQ = 6.5 cm. From the midpoint of line segment PQ, draw a perpendicular
bisector.

Construction of Angles

You already know about angles, types of angles, and how to measure and draw an angle using
protractor. Here, we shall learn how to construct an angle using a ruler and a pair of compasses.
Construction of a Copy of the Given Angle of Unknown Measure

Suppose we have an angle ABC of unknown measure and we need to make A
an angle equal to measure of ∠ABC with the help of a ruler and a pair of
compasses. Following are the steps for the construction of such angle:

Steps of construction:
B C
1. Draw ∠ABC of unknown measure.
2. Draw a line l and mark a point Q on it. Q l

3. Now place the tip of the compass at the vertex 4. Use the same compass setting to draw an
B of the given angle and draw an arc to cut arc with Q as the centre, cutting line l at
the rays (arms) of ∠ABC at D and E. R.

A

D

B E C Q R l

5. Place the needle of the compass on E in 6. Using this setting place the compass
step 3 and adjust the compasses so that the pointer at R and draw an arc to cut the
tip of the pencil is at D. arc drawn earlier at P.

A P
D

B E C Q R

339 Construction of Basic Geometrical Shapes