
Reason: 

Draw a line from the point A as shown. 

Set the compass to create a small arc. Place the spike of the compass at the point A, draw a small arc as shown. 

Keep the same compass setting. Place the spike of the compass at the point where the 1st arc crossed the line, draw a 2nd small arc as shown. 

Keep the same compass setting. Place the spike of the compass at the point where the 2nd arc crossed the line, draw a 3rd small arc as shown. 

Join the point where the 3rd arc crossed the line to the point B. Prepare to construct parallel lines using a set square and a straight edge. 

Construct parallel lines as shown. The line segment [AB] is divided into 3 equal segments. 