Sector, arc and segment
A sector is α/360° of a circle: find its arc length and area, find the angle from the arc length, and find the area of a circular segment.
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Guide
A circular sector is the part of a disc between two radii with the angle α at the centre. It is α/360° of the whole circle.
Arc length: b = α/360° · 2 · π · r. Sector area: A = α/360° · π · r². In this studio we take π ≈ 3.14 and the figures are drawn to scale: 1 cell is 1 cm.
A circular segment is the part of a disc cut off by a chord. For an angle α smaller than 180° the segment is the sector minus the triangle: segment = sector − triangle.