This presentation explains how to determine an unknown segment given that one of its sections forms a golden ratio. The steps are: 1) Draw a square on the known section AB. 2) Find the midpoint M of AB by drawing its perpendicular bisector. 3) Using M as the center and radius MC, draw an arc intersecting the extension of AB at point D. The full segment AD exhibits a golden ratio, with AB as the shorter section.

1. This presentation has been made for you by
FRANCISCO GUIJARRO BELDA
From Isaac Albéniz Secondary School
Leganés. Madrid. Spain.

2. HOW TO WORK OUT A SEGMENT FROM ITS GOLDEN
SECTION
1) Let´s imagine you are given a segment AB and you are told it is the Golden Section
of an unknown segment which you must find out. First step to take is to draw a
square upon AB as you can see in the picture below (if needed, go to the 1st Term
Theory page on the blog to review how to draw a square)

3. 2) Draw the perpendicular bisector of AB in order to determine the middle point of
the segment, labeled by M in the sample

4. 3) Take the compass and place it on point M, radius MC and draw an arch in the
direction you can see in the image

5. 4) Extend the segment AB to the right, so that you can intersect it with the arch you
had already drawn. The result is point D. And that is all, AD is the segment you were
looking for and AB is its Golden Section