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High Quality Content by WIKIPEDIA articles! In geometry, a quadrilateral is a polygon with four 'sides' or edges and four vertices or corners. Sometimes, the term quadrangle is used, for analogy with triangle, and sometimes tetragon for consistency with pentagon (5-sided), hexagon (6-sided) and so on. The word quadrilateral is made of the words quad and lateral. Quad means four and lateral means sides. The interior angles of a quadrilateral add up to 360 degrees of arc.Quadrilaterals are simple (not self-intersecting) or complex (self-intersecting). Simple quadrilaterals are either convex or concave.All convex quadrilaterals tile the plane by repeated rotation around the midpoints of their edges. ... Read more

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This book presents contributions of mathematicians covering topics from ancient India, placing them in the broader context of the history of mathematics. Although the translations of some Sanskrit mathematical texts are available in the literature, Indian contributions are rarely presented in major Western historical works. Yet some of the well-known and universally-accepted discoveries from India, including the concept of zero and the decimal representation of numbers, have made lasting contributions to the foundation of modern mathematics. Through a systematic approach, this book examines these ancient mathematical ideas that were spread throughout India, China, the Islamic world, and Western Europe. ... Read more

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Study of Bråahmasphuòtasiddhåanta, work on ancient Hindu astronomy and mathematics by Brahmagupta, 7th cent. ... Read more