unit circle
a) A circle of radius 1.
b) The circle of radius 1 with centre at the origin, used in defining trigonometric functions.

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• Unit circle — In mathematics, a unit circle is a circle with a unit radius, i.e., a circle whose radius is 1. Frequently, especially in trigonometry, the unit circle is the circle of radius 1 centered at the origin (0, 0) in the Cartesian coordinate system in… …   Wikipedia

• unit circle — noun : a circle whose radius is one unit of length long * * * Math. a circle whose radius has a length of one unit. [1950 55] * * * unit circle or unit sphere, Mathematics. a circle or sphere whose radius is one unit of distance …   Useful english dictionary

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• unit circle — noun Date: 1955 a circle having a radius of 1 …   New Collegiate Dictionary

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• Unit — may refer to:In mathematics: * Unit vector, a vector with length equal to 1 * Unit circle, the circle with radius equal to 1, centered at the origin * Unit interval, the interval of all real numbers between 0 and 1 * Imaginary unit, i , whose… …   Wikipedia

• unit sphere — unit circle or unit sphere, Mathematics. a circle or sphere whose radius is one unit of distance …   Useful english dictionary

• Circle group — For the jazz group, see Circle (jazz band). Lie groups …   Wikipedia