Answer:
The Area of a Segment is the area of a sector minus the triangular piece (shown in light blue here). There is a lengthy reason, but the result is a slight modification of the Sector formula: Area of Segment = θ − sin(θ) 2 × r2 (when θ is in radians) Area of Segment = ( θ × π 360 − sin(θ)2 ) × r2 (when θ is in degrees)