Much has already been written about the golden ratio, φ (see our feature in Tangente 203, 2022). What sets this book apart is its greater focus on mathematics than on symbolism. The first chapter, "The golden ratio," explores the numerical properties of a number that has become a fetish for some. Next comes "The golden rectangle," which surveys its geometric properties. The final chapter, "The golden ratio and the pentagon," highlights the special connections between this polygon and the famous irrational number; it ventures as far as periodic and non-periodic tilings, and even polyhedra, with particular emphasis on the dodecahedron and icosahedron, both of which involve φ.
The book will be rewarding reading for high school students and anyone interested in the connections between geometry and numbers, or between geometry and art. The text of this special issue is taken from the book of the same name in the "Le monde est mathématique" series published by RBA.

Le nombre d’or. Special issue of the daily newspaper Le Monde,

Fernando Corbalán, 116 pages, 2023, 9.99 euros.