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Mathematical Treasure: De Triangulis of Jordanus de Nemore

Frank J. Swetz (The Pennsylvania State University)

Jordanus de Nemore or Jordanus Nemorarius (fl. 13th century) was a French mathematician and scientist who wrote several influential texts on arithmetic, algebra, geometry, and stereographic projection. Little is known of his life other than that he taught briefly at the University of Paris. A manuscript compiled in the period 1350–1569 contains a copy of his De triangulis [On Triangles]. It is now in the British Library’s Harley Manuscript 625 at folios 123r – 130r.

The first page of the text begins on folio 123r of the manuscript:

Various geometric propositions are considered on folio 125v:

Properties of circles are examined on folio 127r:

See images from an early printed copy of Jordanus de Nemore's Arithmetica here in Convergence.

The images above were obtained through the courtesy of the British Library. Each item may be examined in its entirety in the Library’s digital collection under the reference given above.

Index to Mathematical Treasures

Frank J. Swetz (The Pennsylvania State University), "Mathematical Treasure: De Triangulis of Jordanus de Nemore," Convergence (August 2016)