Boyer (1991). «The Arabic Hegemony». A History of Mathematics. էջեր 241–242. «Omar Khayyam (c. 1050–1123), the "tent-maker," wrote an Algebra that went beyond that of al-Khwarizmi to include equations of third degree. Like his Arab predecessors, Omar Khayyam provided for quadratic equations both arithmetic and geometric solutions; for general cubic equations, he believed (mistakenly, as the 16th century later showed), arithmetic solutions were impossible; hence he gave only geometric solutions. The scheme of using intersecting conics to solve cubics had been used earlier by Menaechmus, Archimedes, and Alhazan, but Omar Khayyam took the praiseworthy step of generalizing the method to cover all third-degree equations (having positive roots). .. For equations of higher degree than three, Omar Khayyam evidently did not envision similar geometric methods, for space does not contain more than three dimensions, ... One of the most fruitful contributions of Arabic eclecticism was the tendency to close the gap between numerical and geometric algebra. The decisive step in this direction came much later with Descartes, but Omar Khayyam was moving in this direction when he wrote, "Whoever thinks algebra is a trick in obtaining unknowns has thought it in vain. No attention should be paid to the fact that algebra and geometry are different in appearance. Algebras are geometric facts which are proved."»
Depuydt, Leo (1998 թ․ հունվարի 1). «Gnomons at Meroë and Early Trigonometry». The Journal of Egyptian Archaeology. 84: 171–180. doi:10.2307/3822211. JSTOR3822211.
Depuydt, Leo (1998 թ․ հունվարի 1). «Gnomons at Meroë and Early Trigonometry». The Journal of Egyptian Archaeology. 84: 171–180. doi:10.2307/3822211. JSTOR3822211.
