Editing Regiomontanus (section)

==Work==
[[File:Regiomontanus - De triangulis planis et sphaericis libri, per Henrichum Petri et Petrum Pernam - 4683051.tif|thumb|upright|''De triangulis planis et sphaericis libri'']]
[[File:Houghton Typ Inc 4366 - Regiomontanus 1.jpg|thumb|upright|Title page for ''Qvesta opra da ogni parte e un libro doro'', 1476]]

During his time in Italy he completed Peuerbach's abridgement of ''[[Almagest]]'', ''Epytoma in almagesti Ptolemei''. In 1464, he completed ''De triangulis omnimodis'' ("On Triangles of All Kinds"). ''De triangulis omnimodis'' was one of the first textbooks presenting the current state of [[trigonometry]] and included lists of questions for review of individual chapters. In it he wrote:

{{quote|You who wish to study great and wonderful things, who wonder about the movement of the stars, must read these theorems about triangles. Knowing these ideas will open the door to all of astronomy and to certain geometric problems.}}

In 1465, he built a portable [[sundial]] for [[Pope Paul II]].

In ''Epytoma in almagesti Ptolemei'', he critiqued the translation of ''Almagest'' by [[George of Trebizond]], pointing out inaccuracies. Later [[Nicolaus Copernicus]] would refer to this book as an influence on his own work.

A prolific author, Regiomontanus was internationally famous in his lifetime. Despite having completed only a quarter of what he had intended to write, he left a substantial body of work. [[Nicolaus Copernicus]]' teacher, [[Domenico Maria Novara da Ferrara]], referred to Regiomontanus as having been his own teacher. There is speculation that Regiomontanus had arrived at a theory of heliocentrism before he died; a manuscript shows particular attention to the [[heliocentric]] theory of the [[Pythagoreanism|Pythagorean]] [[Aristarchus of Samos|Aristarchus]], mention was also given to the motion of the earth in a letter to a friend.<ref>[[Arthur Koestler]], ''The Sleepwalkers'', Penguin Books, 1959, p. 212.</ref>

Much of the material on [[spherical trigonometry]] in Regiomontanus' ''On Triangles'' was taken directly{{dubious|date=March 2017}} from the twelfth-century work of [[Jabir ibn Aflah]] otherwise known as Geber, as noted in the sixteenth century by [[Gerolamo Cardano]].<ref>{{Cite book
  | editor = Victor J. Katz
  | title = The mathematics of Egypt, Mesopotamia, China, India, and Islam: a sourcebook
  | publisher = [[Princeton University Press]]
  | date = 2007
  | url = http://press.princeton.edu/chapters/i8583.html
  | isbn = 978-0-691-11485-9
  | access-date = 16 March 2008
  | archive-date = 1 October 2016
  | archive-url = https://web.archive.org/web/20161001214903/http://press.princeton.edu/chapters/i8583.html
  | url-status = dead
  }}, p.4</ref>