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tangent

(Encyclopedia)tangent, in mathematics. 1 In geometry, the tangent to a circle or sphere is a straight line that intersects the circle or sphere in one and only one point. For other curves and surfaces the tangent l...

secant

(Encyclopedia)secant, in mathematics. 1 In geometry, a secant is a straight line cutting a curve or surface. If it intersects the curve in two different points, as in the secant of a circle, the segment of the seca...

Weddell Sea

(Encyclopedia)Weddell Sea wĕdˈəl [key], arm of the Atlantic Ocean, W Antarctica, SE of South America, bordered by the Antarctic Peninsula and Coats Land. The vast Ronne and Filchner ice shelves are at the head o...

Shackleton, Sir Ernest Henry

(Encyclopedia)Shackleton, Sir Ernest Henry, 1874–1922, British antarctic explorer, b. Ireland. The first of his voyages to Antarctica was made as a member of the expedition (1901–4) of Robert F. Scott. Shacklet...

Avebury

(Encyclopedia)Avebury āˈbərē [key], village, Wiltshire, S central England. The village, with a medieval church and Elizabethan manor house, lies within Avebury Circle, a Neolithic circular group of upright ston...

Atlantic Ocean

(Encyclopedia)CE5 Atlantic Ocean [Lat.,=of Atlas], second largest ocean (c.31,800,000 sq mi/82,362,000 sq km; c.36,000,000 sq mi/93,240,000 sq km with marginal seas). The North Atlantic Ocean has some of the w...

Glorioso Islands

(Encyclopedia)Glorioso Islands glōrˌēōˈsō, –zō [key], Fr. Îles Glorieuses, island group, c.2 sq mi (5 sq km), in the Mozambique Channel, W Indian Ocean, 125 mi (200 km) WNW of N Madagascar, part of the Sc...

David, T. W. E.

(Encyclopedia)David, T. W. E. (Sir Tannatt William Edgeworth), 1858–1935, Australian geologist and explorer, b. near Cardiff, Wales. David came to Australia in 1882 as an assistant geological surveyor. In 1891 he...

tern

(Encyclopedia)tern, common name for a sea bird of the Old and New Worlds, smaller than the related gull. Because of their graceful flight and their long pointed wings and forked tails, some terns are called sea swa...

equatorial coordinate system

(Encyclopedia)CE5 Equatorial coordinate system equatorial coordinate system, the most commonly used astronomical coordinate system for indicating the positions of stars or other celestial objects on the celesti...