Question

Construct ${120}^{\circ }$ using a ruler and a compass.

Answer 1

Steps of construction:

(i) Draw a ray $\overline{OA}$
(ii) Taking $O$ as centre and convenient radius, mark an arc, which intersects $\overline{OA}$ at $P$.
(iii) Taking $P$ as centre and same radius, cut previous arc at $Q$.
(iv) Taking $Q$ as centre and same radius cut the arc at $S$.
(v) Join $OS$ and extend it to point $D$. Thus, $\angle AOD$ is the required angle of ${120}^{\circ }$.