Arc: Length

How to find the length of an arc: formula, 1 example, and its solution.

Formula

Formula

l = 2πr⋅[θ/360]

l: Length of an arc
r: Radius
θ: Central angle (in degrees)

2πr is the circumference of the whole circle.
θ/360 is the ratio of arc/circle.

Example

Example

Solution

r = 6
θ = 120º

l = 2π⋅6⋅[120/360]

2π⋅6 = 12π
120/360 = 1/3

12⋅[1/3] = 4

So 4π is the answer.