Bride's Chair
Introduction

[150px\|thumb\|right\|Bride's Chair: Illustration of Pythagorean theorem](/wiki/File:Brides_Chair_02.png "Brides Chair 02.png")
[thumb\|150px\|Bride's Chair: The figure used by Euclid to explain the proof of Pythagorean theorem](/wiki/File:Brides_Chair_01.png "Brides Chair 01.png")
In [geometry](/wiki/Geometry "Geometry"), a **Bride's Chair** is an illustration of the [Pythagorean theorem](/wiki/Pythagorean_theorem "Pythagorean theorem"). The figure appears in Proposition 47 of Book I of [Euclid's Elements](/wiki/Euclid%27s_Elements "Euclid's Elements"). It is also known by several other names, such as the **Franciscan's cowl**, **peacock's tail**, **windmill**, **Pythagorean pants**, **Figure of the Bride**, **theorem of the married women**, and **chase of the little married women**.

According to Swiss\-American historian of mathematics [Florian Cajori](/wiki/Florian_Cajori "Florian Cajori"), the ultimate etymology of the term "Bride's Chair" lies in a Greek [homonym](/wiki/Homonym "Homonym"): "Some Arabic writers \[...] call the Pythagorean theorem 'figure of the bride'." The Greek word  has two relevant definitions: 'bride', and 'winged insect'. The figure of a right triangle with the three squares has reminded various writers of an insect, so the 'insect' sense of the Greek word came to be applied to right triangles with three squares, and to the Pythagorean theorem. Arabic speakers writing in Greek would often mistakenly assume the other sense of the word was intended, and would translate the phrase back into Arabic using the word for 'bride'.

A nice illustration of the Bride's Chair showing a chair upon which, according to ancient tradition, a bride might have been carried to the marriage ceremony can be seen in Sidney J. Kolpas' *The Pythagorean Theorem: Eight Classic Proofs* (page 3\).


How does the concept of the Bride's Chair apply to modern society?