This article is about Hypsicles of Alexandria. For the historian, see Hyspicrates (historian).
Hypsicles (Ancient Greek: Ὑψικλῆς; ca. 190 BCE  ca. 120 BCE) was an ancient Greek mathematician and astronomer known for authoring De ascensionibus and the spurious Book XIV of Euclid's Elements.
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Although little is known about the life of Hypsicles, it is believed that he authored the astronomical work De ascensionibus. In this work, Hypsicles proves a number of propositions on arithmetical progressions and uses the results to calculate approximate values for the times required for the signs of the zodiac to rise above the horizon.^{[1]} It is thought that this is the work from which the division of the circle into 360 parts may have been adopted^{[2]} since it divides the day into 360 parts, a division possibly suggested by Babylonian astronomy.^{[3]}
Hypsicles is more famously known for possibly writing the apocryphal Book XIV of Euclid's Elements. The spurious Book XIV may have been composed on the basis of a treatise by Apollonius. The book continues Euclid's comparison of regular solids inscribed in spheres, with the chief result being that the ratio of the surfaces of the dodecahedron and icosahedron inscribed in the same sphere is the same as the ratio of their volumes, the ratio being .^{[2]}


