Draw a line segment AB and bisect it. Also, bisect one of the equal parts.
Answer:
Draw a line segment AB. With center A and radius more than half of AB, draw arcs one on each side of AB. With center B and same radius, draw arcs cutting previous arcs at P and Q respectively. Join PQ and which intersect AB at C. With center A and radius more than half of AC, draw arcs on each side of AC. With center C and same radius, draw arcs cutting previous arcs at R and S respectively. Join RS and which intersect AC at D.