Book III

contains genuine spherical trigonometry, consisting of 'Menelaus's Theorem' with reference to the sphere and deductions therefrom.

Ptolemy's great work, the _Syntaxis_, written about A. D. 150 and originally called Μαθηματικη συνταξις {Mathêmatikê syntaxis}, came to be known as Μεγαλη συνταξις {Megalê syntaxis}; the Arabs made up from the superlative μεγιστος {megistos} the word al-Majisti which became _Almagest_.