Chapter 19: Geometrical Constructionss Exercise 19.4

Question: 1

Construct the following angles with the help of protractor:

45^°, 67^°, 38^°, 110^°, 179^°, 98^°, 84^°.

Solution:

We draw a ray OA.

We place the protractor on OA such that its center coincides with the point 0 and the diameter of the protractor coincides with OA.

We mark a point B against the mark of 45° on the protractor.

We remove the protractor and draw OB. ∠AOB is the required angle of 45°.

Similarly, we draw the angles 67^°, 38^°, 110^°, 179^°, 98^° and 84°.

Question: 2

Draw two rays PQ and RS as shown in figure. Using the protractor, construct angles of 15^° and 138^° with one arm PQ and RS respectively.

Solution:

(i) Draw a ray PQ as given in the question.

Place the protractor on the ray PQ such that its center coincides with the point P and the diameter of the protractor coincides with PQ.

Mark a point B against the mark of 15° on the protractor.

Remove the protractor and draw PB. ∠QPB is the required angle of 15°.

(ii) Draw a ray RS as given in the question.

Place the protractor on ray RS such that its centre coincides with the point R and diameter of the protractor coincides with RS.

Mark a point T against the mark of 138^° on the protractor.

Remove the protractor and draw RJ.

∠SRTIIs the required angle of 138^°.