"On the Divine Proportion", is a book of mathematics written by Luca Pacioli and illustrated by Leonardo da Vinci, composed around 1498 in Milan and first printed in 1509. Its subject was mathematical proportions (the title refers to the golden ratio) and their applications to geometry, visual art through perspective, and architecture. The clarity of the written material and Leonardo's excellent diagrams helped the book to achieve an impact beyond mathematical circles, popularizing contemporary geometric concepts and images.

This is where Revel Design Studio drew its inspiration for its logo. The Architectural Alphabet was hand drawn by Leonardo with a ruler and a compass and is composed of 23 capitol letters.

In mathematics, two quantities are in the **golden ratio** if their ratio is the same as the ratio of their sum to the larger of the two quantities. The figure on the right illustrates the geometric relationship. Expressed algebraically, for quantities *a* and *b* with *a* > *b* > 0,

a+ba=ab =def φ,

where the Greek letter phi (φ or ϕ) represents the golden ratio. Its value is:

φ=1+52=1.6180339887…. A001622

As humans we respond to this golden ratio or golden section as it is often called, very well. It appears in nature as fractals in plants, seashells, snowflakes and crystals as well as others. It is something that offers peace and balance on a subconscious level.