Calculate the area of a circular segment (sector minus triangle) from radius and angle.
A circular segment is the region between a chord and the arc it subtends. Its area equals the sector area minus the triangular area formed by the two radii and the chord.
Segment Area
A = ½ × r² × (θ − sin θ)
For a semicircle (180°), the segment is the upper half of the circle. The formula still applies.
For angles > 180° the formula gives the major segment area directly.