An Etymological Dictionary of Astronomy and Astrophysics
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A trigonometric function giving the ratio of the side adjacent to a given angle to the hypotenuse.

Mod.L. complementi sinus, → com-; → sine.

A function, denoted cosh x, defined for all real values of x, by the relation: cosh x = (1/2) (e^x + e^-x).

→ hyperbolic; → cosine.

The intensity of the light emanating in any given direction from a perfectly diffusing surface is proportional to the cosine of the angle between the direction and the normal to the surface. Also called → Lambert's law.

→ lambert; → cosine; → law.

An expression that for any triangle relates the length of a side to the cosine of the opposite angle and the lengths of the two other sides. If a, b, and c are the sides and A, B, and C are the corresponding opposites angles: a² = b² + c² - 2bc cos A; b² = c² + a² - 2ca cos B; c² = a² + b² - 2ab cos C.

→ law; → cosine.