Question

Construct with ruler and compass, angle of 120° measure.

Answer 1

The below given steps will be followed to construct an angle of 120°.

1. Draw a line l and mark a point P on it. Now taking P as centre and with a convenient radius, draw an arc of a circle which intersects line l at Q.
2. Taking Q as centre and with the same radius as before, draw an arc intersecting the previously drawn arc at R. 
3. Taking R as centre and with the same radius as before, draw an arc intersecting the arc at S (see figure).
4. Join PS, which is the required ray making 120° with line l.