Page 212 - Start Up Mathematics_7

Steps of Construction:
1. Draw a line segment BC = 3.9 cm.

2. Construct ∠CBX = 90º (Fig. 1). B 3.9 cm C

X X
A

5 cm

B 3.9 cm C B 3.9 cm C
Fig. 1 Fig. 2
3. Taking C as centre, draw an arc with radius 5 cm to intersect BX at A (Fig. 2).
4. Join AC to obtain the required ∆ ABC.
Example 8: Construct an isosceles right-angled ∆ ABC, where ∠ACB = 90° and AC = 3 cm.
Solution: Construction: Draw a rough sketch of the isosceles right-angled A
triangle ABC in which BC = AC = 3 cm and ∠ACB = 90°.
3 cm
Steps of Construction:
1. Draw a line segment BC = 3 cm. B 3 cm C

2. Construct ∠BCX = 90º (Fig. 1). B 3 cm C

X A X

3 cm

B 3 cm C B 3 cm C
Fig. 1 Fig. 2
3. Taking C as centre and opening of 3 cm draw an arc to intersect CX at point A.
4. Join AB to obtain the required isosceles right-angled triangle ABC (Fig. 2).

EXERCISE

1. Draw a line AB and take a point P outside it. Draw another line CD parallel to AB, which
passes through point P.
2. Draw a line AB and take a point P that is 5 cm away from it. Draw another line CD parallel
to AB, which passes through point P.

3. Given a line l, draw another line m parallel to l at a distance of 4.6 cm from it.
4. Construct a ∆ ABC in which BC = 6 cm, AB = 5 cm and AC = 5.5 cm.
5. Construct a ∆ ABC in which BC = 4.5 cm, AB = 5.3 cm and AC = 5 cm.

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