Unit circle

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Illustration o a unit circle. The variable t is an angle measur.

In mathematics, a unit circle is a circle wi a radius o ane. Frequently, especially in trigonometry, the unit circle is the circle o radius ane centred at the origin (0, 0) in the Cartesian coordinate system in the Euclidean plane. The unit circle is eften denotit S1; the generalization tae heicher dimensions is the unit sphere.