Diagram, triangle by unknown author Diagram contained in text on the third page of the document. Illustrates a right angle triangle positioned upside down. Angles are drawn across it. Parts are lettered. Subject: Geometry Published in Philosophical Transactions as 'Responsio ad animadversionem ad Davidis Gregorii Catenariam, act. Eruditorum lipsiæ. Mense Februarii an. 1699'. Read to the Royal Society on 24 January 1699. [1699]