- Books Name
- CBSE Class 6 Mathematics Book

- Publication
- Param Publication

- Course
- CBSE Class 6

- Subject
- Mathmatics

**Construction of Special Angles **

**Constructing a 60° angle**

**Step 1 ** Draw a line l and mark a point O on it.

**Step 2** Place the pointer of the compasses at O and draw an arc of convenient radius which cuts the line PQ at a point say, A.

**Step 3** With the pointer at A (as centre), now draw an arc that passes through O.

**Step 4 ** Let the two arcs intersect at B. Join OB. We get *∠*BOA whose measure is 60°.

**Constructing a 30° angle**

Construct an angle of 60° as shown earlier. Now, bisect this angle. Each angle is 30°, verify by using a protractor.

**Constructing a 120° angle**

An angle of 120° is nothing but twice of an angle of 60°. Therefore, it can be constructed as follows :

** Step 1 ** Draw any line PQ and take a point O on it.

**Step 2 ** Place the pointer of the compasses at O and draw an arc of convenient radius which cuts the line at A.

**Step 3 ** Without disturbing the radius on the compasses, draw an arc with A as centre which cuts the first arc at B.

**Step 4 ** Again without disturbing the radius on the compasses and with B as centre, draw an arc which cuts the first arc at C.

**Step 5 ** Join OC, *∠*COA is the required angle whose measure is 120°.

**Constructing a 90° angle**

**Step 1** With A as centre and any suitable radius draw an arc cutting AB at P.

**Step 2** With P as centre and the same radius as before cut the arc of Step 1 at Q. With Q as centre and the same radius cut the arc again at R.

**Step 3 ** With Q and R as centres and any convenient radius (same for both) draw arcs cutting at S. Join A to S and produce A to L. Then *∠*BAL = 90°, i.e., AL is perpendicular to AB at A.