Question

Draw an angle of 80° with the help of a protractor. Then construct angles of (i) 40° (ii) 160° and (iii) 120°.

Answer 1

First, draw an angle of 80° say ∠QOA = 180° with the help of protractor.

Now, use the following steps to construct angles of (i) 40° (ii) 160° (iii) 120°

1. Taking O as centre and any radius draw an arc which intersect OA at E and OO at F.

2. Taking E and F as centres and radius more than `1/2` EF draw arcs which intersect each other at P.

3. Join OP. Thus, ∠POA = 40°  ...`[∴ 40^circ = 1/2 xx 80^circ]`

4. Now, taking F as centre and radius equal to EF draw an arc which intersect previous arc obtained in step ii at S.

5. Join OS. Thus, ∠SOA = 160°  ...[∴ 160° = 2 × 80°]

6. Taking S and F as centre and radius more than `1/2` SF draw arcs which intersect each other at R.

7. Join OR. Thus, ∠ROA = ∠ROQ = 40° + 80° = 120°.