sphere: Quick Facts

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The normal, or perpendicular, at each point of a surface defines the corresponding tangent plane, and vice versa.

A red sphere fits perfectly inside a transparent blue cylinder, illustrating Archimedes' relationship between the surface area and volume of a sphere and its circumscribing cylinder, with labeled formulas and dimensions.

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Topics

Poincaré conjecture spherical triangle Ewald’s sphere pseudosphere geodesic rhumb line ellipsoid cone cylinder paraboloid hyperboloid

Key People

Portrait of Archimedes by Giuseppe Nogari shows an elderly man with white hair and beard, holding a compass, gazing downward, set against a dark background.

Archimedes

Greek mathematician and inventor

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Menelaus of Alexandria

Greek mathematician

Equations written on blackboard

Numbers and Mathematics