Circle+Formulae

Circle Formula

The ratio of a circle's [|circumference] to its [|diameter] is [|π] (pi), a [|constant] that takes the same value (approximately 3.141592654) for all circles. Thus the length of the circumference (//c//) is related to the radius (//r//) by or equivalently to the diameter (//d//) by Using the circle constant τ = 2π  one gets As proved by Archimedes the area of the [|area enclosed by a circle] is. Equivalently, the area is π  multiplied by the radius squared:

Using the circle constant τ = 2π  one gets