REGIOMONTANUS, Iohannes.

by Iohannes Regiomontanus

£12,500 · Offered by Sokol Books

A very handsome copy of the rare enlarged third edition; De triangulis was Regiomontanus s most important scientific contribution. Completed in 1464, it remained in manuscript for nearly seventy years before being published in 1533 in Nuremberg by Johann Petri. It contains the earliest statement of the cosine law for spherical triangles, stating the proportionality of the sides of a plane triangle to the sines of the opposite angle. This fundamental proposition of spherical trigonometry appears as theorem 2 in book V of the treatise. In the second part, Regiomontanus proves the errors of Nicolaus de Cusa s theory of squaring the circle, which had a profound effect on the history of navigation. The first systematic treatise on plane and spheric trigonometry to be published in Europe. Although it drew heavily on Arabic sources, those earlier treatises had been either lost or forgotten by 1533 when Regiomontanuss work was first printed. Among the notable contents of this work are the sine law and perhaps the first European application of algebra to trigonometry. Indeed with De triangulis trigonometry was established as an independent discipline. Regiomontanus original purpose, however, had been to furnish astronomers with a mathematical technique essential for their studies, and in this De triangulis had a success perhaps greater than its author could have dreamed of. For in 1539 Georg Joachim Rheticus presented a copy of the work s 1533 edition as a gift to Copernicus. The grea

• Binding: Hardcover

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