A Simple Construction of the Golden Ratio
Abstract. We construct the golden ratio by using an area bisector of a trapezoid.
Consider a trapezoid PQRS with bases PQ = b, RS = a, a < b. Assume, in
Figure 1, that the segment MN of length
a2+b2
2 is parallel to PQ. Then MN
lies between the bases PQ and RS (see [1, p.57]). It is easy to show that MN
bisects the area of the trapezoid. It is more interesting to note thatM and N divide
SP and RQ in the golden ratio if b = 3a. To see this, construct a segment SW
parallel to RQ and let V = MN ∩ SW. It is clear that