Draw an obtuse angle. Bisect it. Measure each of the angles so formed.
Steps of construction:
1. Draw an angle ∠ABC of 120°.
2. With B as a centre and any radius, draw an arc which intersects AB at P and BC at Q.
3. With P as center and radius more than half of PQ draw an arc.
4. With Q as a center and same radius draw an arc which cuts the previous arc at R.
5. Join BR.
Therefore ∠ABR = ∠RBC = 60°