"was among the first to take advantage of the recovery of the original texts of the Greek mathematical works... the earliest notice in modern Europe of the algebra of Diophantus is [his] remark... that he had seen a copy... at the Vatican. He was also well read in the works of the Arab mathematicians. The fruit of this study... his De Triangulis... 1464... the earliest modern systematic exposition of trigonometry, plane and spherical, though the only trigonometrical functions introduced are... the sine and cosine. It is divided into five books. The first four... plane trigonometry... in particular... determining triangles from three given conditions. The fifth book is... spherical trigonometry. The work was printed in five volumes... 1533, nearly a century after the death of Regiomontanus."