Math Playground
Geometry

Arc

A piece of a circle's circumference — measured by angle or by length.

An arc is a piece of a circle's circumference.

Arc length
L = r·θ (θ in radians)
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Arc length of a 90° arc on a circle radius 10

θ = π/2. L = 10 × π/2 = 5π ≈ 15.7.