Page 267 - Start Up Mathematics_6

Construction of an angle of measure 90°

1. Draw a ray OX. O X

2. With O as centre, draw an arc of any
radius cutting OX at A. O A X

3. With A as centre and same opening (i.e., OA), C
draw an arc cutting the previously drawn arc at B

B. Further with B as centre and same opening, O A X
cut the same arc again at C.

Y
D
4. With B and C as centres and convenient radius
(same for both) draw two arcs cutting each other
at D.
C B
5. Join O and D to obtain the angle of measure 90°,
i.e., ∠XOY = 90°. O X

An angle of 45° can be obtained by first constructing an angle of measure 90° and then bisecting it.

EXERCISE 14.3

1. Draw an angle of measure 84° and construct its angle bisector.

2. Draw an angle of measure 100°. Make a copy of it using a ruler and compass only.

3. With a ruler and compass only construct each of the following angles:

(a) 30° (b) 120° (c) 45° (d) 135° (e) 150°

MATHS LAB ACTIVITY

Draw an angle of measure 45°. Draw two
rays in its interior to form three angles each B
of measure 15°, using a ruler and compass D
only. 15°
15° C
[Hint: Draw an angle of 60° and bisect it.] O 15° A

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