Editing Ellipse (section)

===Pins-and-string method===
The characterization of an ellipse as the locus of points so that sum of the distances to the foci is constant leads to a method of drawing one using two [[drawing pin]]s, a length of string, and a pencil. In this method, pins are pushed into the paper at two points, which become the ellipse's foci. A string is tied at each end to the two pins; its length after tying is <math>2a</math>. The tip of the pencil then traces an ellipse if it is moved while keeping the string taut. Using two pegs and a rope, gardeners use this procedure to outline an elliptical flower bed—thus it is called the ''gardener's ellipse''. The Byzantine architect [[Anthemius of Tralles]] ({{c.|600}}) described how this method could be used to construct an elliptical reflector,<ref>From {{lang|el|Περί παραδόξων μηχανημάτων}} [''Concerning Wondrous Machines'']: "If, then, we stretch a string surrounding the points A, B tightly around the first point from which the rays are to be reflected, the line will be drawn which is part of the so-called ellipse, with respect to which the surface of the mirror must be situated." {{pb}} {{cite book |last=Huxley |first=G. L. |year=1959 |title=Anthemius of Tralles: A Study in Later Greek Geometry |lccn=59-14700 |location=Cambridge, MA |pages=8–9 |url=https://archive.org/details/anthemiusoftrall0000huxl/page/8/ |url-access=limited }}</ref> and it was elaborated in a now-lost 9th-century treatise by [[Al-Ḥasan ibn Mūsā ibn Shākir|Al-Ḥasan ibn Mūsā]].<ref>Al-Ḥasan's work was titled {{transliteration|ar|Kitāb al-shakl al-mudawwar al-mustaṭīl}} [''The Book of the Elongated Circular Figure'']. {{pb}} {{cite book |last1=Rashed |first1=Roshdi |translator-last=Shank |translator-first=Michael H. |title=Classical Mathematics from Al-Khwarizmi to Descartes |date=2014 |publisher=Routledge |location=New York |isbn=978-13176-2-239-0 |page=559 }}</ref>

A similar method for drawing [[Confocal conic sections#Graves's theorem: the construction of confocal ellipses by a string|confocal ellipses]] with a ''closed'' string is due to the Irish bishop [[Charles Graves (bishop)|Charles Graves]].