Circle

Circumference of a circle

$C = 2\cdot \pi\cdot R$

R - radius of a circle

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Circumference of a circle (by diameter)

$C = \pi\cdot d$

d - diameter of a circle

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Length of an arc of a circle‎

$l = \frac{\pi\cdot R\cdot \alpha}{180}$

R - radius of a circle
α - central angle

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Length of a chord of a circle‎

$AB = 2\cdot R\cdot sin(\alpha)$

R - radius of a circle
α - central angle

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