Page 261 - Start Up Mathematics_6

Construction of a Line Segment of Given Length
Let’s draw a line segment of length 3.5 cm.
One way to draw a line segment is to mark a point A on the
ruler coinciding with 0 and the other point B coinciding with A B
3.5 mark. Join A and B to get the line segment of length 3.5 cm.
A better method using a ruler and compass is given as follows:

Steps of construction A
1. Draw a line l and mark any point A on it. l
2. Place the pointed end of the compass at zero mark of the
ruler and open it so that the pencil end reaches 3.5 cm mark.
3. Without changing the opening of the compass, place the
pointed end of the compass at A and draw an arc to cut line
l at B. l
4. AB is the line segment of the required length. A 3.5 cm B

The above method can also be used to draw a line segment of length equal to the length of the given
line segment.

EXERCISE 14.1

1. Draw a circle of radius 2.8 cm.
2. Draw a circle of radius 4 cm. Draw another circle concentric with it of radius 5 cm.
3. Draw a circle and any two of its diameters. What figure is obtained by joining the ends
of these diameters?
4. Construct a line segment measuring 7.3 cm using (a) ruler only, (b) ruler and compass.
5. Draw a line segment of length 6.8 cm using a ruler. Construct another line segment of the
same length using a ruler and compass.
6. Construct a line segment of length 4.2 cm. Use a ruler and compass to draw another line
segment double its length.
7. Draw any line segment AB. Without measuring AB construct another line segment of the
same length.

Construction of a Perpendicular to a Given Line on a Point Lying on It
Let’s learn how to draw a perpendicular on point P lying P l
on the given line l in two different ways: P
l
Using a ruler and set square

1. Place a ruler along line l having a
given point P on it.

2. Keeping the ruler firm, place the set square above the
ruler such that its right-angled vertex is in contact P
with the ruler. l

3. Slide the set square along the edge of the ruler until
its right-angled vertex coincides with P.

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