polygonal number
61Architecture of the medieval cathedrals of England — The medieval cathedrals of England, dating from between approximately 1040 and 1540, are a group of twenty five buildings which together constitute a major aspect of the country’s artistic heritage and are among the most significant material… …
62Diophantus — For the general, see Diophantus (general). Title page of the 1621 edition of Diophantus Arithmetica, translated into Latin by Claude Gaspard Bachet de Méziriac. Diophantus of Alexandria (Greek: Διόφαντος ὁ Ἀλεξανδρεύς XD. b. between 200 and 214… …
63Islamic arts — Visual, literary, and performing arts of the populations that adopted Islam from the 7th century. Islamic visual arts are decorative, colourful, and, in religious art, nonrepresentational; the characteristic Islamic decoration is the arabesque.… …
64keyboard instrument — ▪ music Introduction any musical instrument on which different notes can be sounded by pressing a series of keys, push buttons, or parallel levers. In nearly all cases in Western music the keys correspond to consecutive notes in the… …
65JERUSALEM — The entry is arranged according to the following outline: history name protohistory the bronze age david and first temple period second temple period the roman period byzantine jerusalem arab period crusader period mamluk period …
66Church architecture — The 800 year old Church of Termunterzijl in the north of the Netherlands See also: Architecture of cathedrals and great churches Church architecture refers to the architecture of buildings of Christian churches. It has evolved over the two… …
67Castle — This article is about medieval fortifications. For other uses, see Castle (disambiguation). For a list of all castles, see List of castles. For similar but unrelated structures in Japan, see Japanese castle …
68Round barn — A round barn is a historic barn design that could be octagonal, polygonal, or circular in plan. Numerous round barns in the United States are listed on the National Register of Historic Places. Though round barns were not as popular as some other …
69permafrost — /perr meuh frawst , frost /, n. (in arctic or subarctic regions) perennially frozen subsoil. Also called pergelisol. [1943; PERMA(NENT) + FROST] * * * Perennially frozen earth, with a temperature below 32 °F (0 °C) continuously for two years or… …
70Arc length — Determining the length of an irregular arc segment is also called rectification of a curve. Historically, many methods were used for specific curves. The advent of infinitesimal calculus led to a general formula that provides closed form… …
