Draw a line AB. At A, draw an arc of length 3cm using compass such that it intersects AB at O. With the same spread of compass, put the compass pointer at O and make an arc that intersects the previous arc at P. With the same spread again, put the compass pointer at P and draw an arc that intersects the first arc at Q. Join A and Q. Using the protractor, measure ∠QAB. What is the measure of ∠QAB ?
120∘
Following all the steps mentioned, we obtain the following
On measuring ∠QAB, we would get the measure of the angle equal to 120∘.